From 218934fa2ed1c702a6d3923d2aa2cc6b43c48684 Mon Sep 17 00:00:00 2001 From: Peter Bengtsson Date: Tue, 8 Dec 2020 14:43:23 -0500 Subject: initial commit --- .../reference/global_objects/math/abs/index.html | 104 ++++++++++ .../reference/global_objects/math/ceil/index.html | 170 +++++++++++++++++ .../reference/global_objects/math/floor/index.html | 169 ++++++++++++++++ .../reference/global_objects/math/index.html | 196 +++++++++++++++++++ .../reference/global_objects/math/max/index.html | 117 ++++++++++++ .../reference/global_objects/math/pow/index.html | 107 +++++++++++ .../global_objects/math/random/index.html | 95 +++++++++ .../reference/global_objects/math/round/index.html | 212 +++++++++++++++++++++ 8 files changed, 1170 insertions(+) create mode 100644 files/zh-tw/web/javascript/reference/global_objects/math/abs/index.html create mode 100644 files/zh-tw/web/javascript/reference/global_objects/math/ceil/index.html create mode 100644 files/zh-tw/web/javascript/reference/global_objects/math/floor/index.html create mode 100644 files/zh-tw/web/javascript/reference/global_objects/math/index.html create mode 100644 files/zh-tw/web/javascript/reference/global_objects/math/max/index.html create mode 100644 files/zh-tw/web/javascript/reference/global_objects/math/pow/index.html create mode 100644 files/zh-tw/web/javascript/reference/global_objects/math/random/index.html create mode 100644 files/zh-tw/web/javascript/reference/global_objects/math/round/index.html (limited to 'files/zh-tw/web/javascript/reference/global_objects/math') diff --git a/files/zh-tw/web/javascript/reference/global_objects/math/abs/index.html b/files/zh-tw/web/javascript/reference/global_objects/math/abs/index.html new file mode 100644 index 0000000000..91be97bc11 --- /dev/null +++ b/files/zh-tw/web/javascript/reference/global_objects/math/abs/index.html @@ -0,0 +1,104 @@ +--- +title: Math.abs() +slug: Web/JavaScript/Reference/Global_Objects/Math/abs +tags: + - JavaScript + - Math + - Method + - Reference +translation_of: Web/JavaScript/Reference/Global_Objects/Math/abs +--- +
{{JSRef}}
+ +

Math.abs() 函式會回傳一個數字的絕對值，即為：

+ +

Math.abs(x)=|x|={xifx>00ifx=0-xifx<0{\mathtt{\operatorname{Math.abs}(x)}} = {|x|} = \begin{cases} x & \text{if} \quad x \geq 0 \\ x & \text{if} \quad x < 0 \end{cases}

+ +
{{EmbedInteractiveExample("pages/js/math-abs.html")}}
+ + + +

語法

+ +
Math.abs(x)
+ +

參數

+ +
+
x
+
一個數字。
+
+ +

回傳值

+ +

給定數字的絕對值。

+ +

描述

+ +

Because abs() is a static method of Math, you always use it as Math.abs(), rather than as a method of a Math object you created (Math is not a constructor).

+ +

範例

+ +

Math.abs() 的行為

+ +

Passing an empty object, an array with more than one member, a non-numeric string or {{jsxref("undefined")}}/empty variable returns {{jsxref("NaN")}}. Passing {{jsxref("null")}}, an empty string or an empty array returns 0.

+ +
Math.abs('-1');     // 1
+Math.abs(-2);       // 2
+Math.abs(null);     // 0
+Math.abs('');       // 0
+Math.abs([]);       // 0
+Math.abs([2]);      // 2
+Math.abs([1,2]);    // NaN
+Math.abs({});       // NaN
+Math.abs('string'); // NaN
+Math.abs();         // NaN
+
+ +

規範

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
SpecificationStatusComment
{{SpecName('ES1')}}{{Spec2('ES1')}}Initial definition. Implemented in JavaScript 1.0.
{{SpecName('ES5.1', '#sec-15.8.2.1', 'Math.abs')}}{{Spec2('ES5.1')}} 
{{SpecName('ES6', '#sec-math.abs', 'Math.abs')}}{{Spec2('ES6')}} 
{{SpecName('ESDraft', '#sec-math.abs', 'Math.abs')}}{{Spec2('ESDraft')}} 
+ +

瀏覽器相容性

+ + + +

{{Compat("javascript.builtins.Math.abs")}}

+ +

參見

+ + diff --git a/files/zh-tw/web/javascript/reference/global_objects/math/ceil/index.html b/files/zh-tw/web/javascript/reference/global_objects/math/ceil/index.html new file mode 100644 index 0000000000..7ce7174f0b --- /dev/null +++ b/files/zh-tw/web/javascript/reference/global_objects/math/ceil/index.html @@ -0,0 +1,170 @@ +--- +title: Math.ceil() +slug: Web/JavaScript/Reference/Global_Objects/Math/ceil +tags: + - JavaScript + - Math + - Method + - Reference +translation_of: Web/JavaScript/Reference/Global_Objects/Math/ceil +--- +
{{JSRef}}
+ +

Math.ceil() 函式會回傳大於等於所給數字的最小整數。

+ +
{{EmbedInteractiveExample("pages/js/math-ceil.html")}}
+ + + +

語法

+ +
Math.ceil(x)
+ +

參數

+ +
+
x
+
一個數字。
+
+ +

回傳值

+ +

一個大於等於指定數字的最小整數。

+ +

描述

+ +

Because ceil() is a static method of Math, you always use it as Math.ceil(), rather than as a method of a Math object you created (Math is not a constructor).

+ +

範例

+ +

使用 Math.ceil()

+ +

The following example shows example usage of Math.ceil().

+ +
Math.ceil(.95);    // 1
+Math.ceil(4);      // 4
+Math.ceil(7.004);  // 8
+Math.ceil(-0.95);  // -0
+Math.ceil(-4);     // -4
+Math.ceil(-7.004); // -7
+
+ +

Decimal adjustment

+ +
// Closure
+(function() {
+  /**
+   * Decimal adjustment of a number.
+   *
+   * @param {String}  type  The type of adjustment.
+   * @param {Number}  value The number.
+   * @param {Integer} exp   The exponent (the 10 logarithm of the adjustment base).
+   * @returns {Number} The adjusted value.
+   */
+  function decimalAdjust(type, value, exp) {
+    // If the exp is undefined or zero...
+    if (typeof exp === 'undefined' || +exp === 0) {
+      return Math[type](value);
+    }
+    value = +value;
+    exp = +exp;
+    // If the value is not a number or the exp is not an integer...
+    if (isNaN(value) || !(typeof exp === 'number' && exp % 1 === 0)) {
+      return NaN;
+    }
+    // Shift
+    value = value.toString().split('e');
+    value = Math[type](+(value[0] + 'e' + (value[1] ? (+value[1] - exp) : -exp)));
+    // Shift back
+    value = value.toString().split('e');
+    return +(value[0] + 'e' + (value[1] ? (+value[1] + exp) : exp));
+  }
+
+  // Decimal round
+  if (!Math.round10) {
+    Math.round10 = function(value, exp) {
+      return decimalAdjust('round', value, exp);
+    };
+  }
+  // Decimal floor
+  if (!Math.floor10) {
+    Math.floor10 = function(value, exp) {
+      return decimalAdjust('floor', value, exp);
+    };
+  }
+  // Decimal ceil
+  if (!Math.ceil10) {
+    Math.ceil10 = function(value, exp) {
+      return decimalAdjust('ceil', value, exp);
+    };
+  }
+})();
+
+// Round
+Math.round10(55.55, -1);   // 55.6
+Math.round10(55.549, -1);  // 55.5
+Math.round10(55, 1);       // 60
+Math.round10(54.9, 1);     // 50
+Math.round10(-55.55, -1);  // -55.5
+Math.round10(-55.551, -1); // -55.6
+Math.round10(-55, 1);      // -50
+Math.round10(-55.1, 1);    // -60
+// Floor
+Math.floor10(55.59, -1);   // 55.5
+Math.floor10(59, 1);       // 50
+Math.floor10(-55.51, -1);  // -55.6
+Math.floor10(-51, 1);      // -60
+// Ceil
+Math.ceil10(55.51, -1);    // 55.6
+Math.ceil10(51, 1);        // 60
+Math.ceil10(-55.59, -1);   // -55.5
+Math.ceil10(-59, 1);       // -50
+
+ +

規範

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
SpecificationStatusComment
{{SpecName('ES1')}}{{Spec2('ES1')}}Initial definition. Implemented in JavaScript 1.0.
{{SpecName('ES5.1', '#sec-15.8.2.6', 'Math.ceil')}}{{Spec2('ES5.1')}} 
{{SpecName('ES6', '#sec-math.ceil', 'Math.ceil')}}{{Spec2('ES6')}} 
{{SpecName('ESDraft', '#sec-math.ceil', 'Math.ceil')}}{{Spec2('ESDraft')}} 
+ +

瀏覽器相容性

+ + + +

{{Compat("javascript.builtins.Math.ceil")}}

+ +

參見

+ + diff --git a/files/zh-tw/web/javascript/reference/global_objects/math/floor/index.html b/files/zh-tw/web/javascript/reference/global_objects/math/floor/index.html new file mode 100644 index 0000000000..5587d60838 --- /dev/null +++ b/files/zh-tw/web/javascript/reference/global_objects/math/floor/index.html @@ -0,0 +1,169 @@ +--- +title: Math.floor() +slug: Web/JavaScript/Reference/Global_Objects/Math/floor +tags: + - JavaScript + - Math + - Method + - Reference +translation_of: Web/JavaScript/Reference/Global_Objects/Math/floor +--- +
{{JSRef}}
+ +

Math.floor() 函式會回傳小於等於所給數字的最大整數。

+ +
{{EmbedInteractiveExample("pages/js/math-floor.html")}}
+ + + +

語法

+ +
Math.floor(x)
+ +

參數

+ +
+
x
+
數字型態。
+
+ +

回傳值

+ +

小於等於所給數字的最大整數。

+ +

描述

+ +

 floor() 是 Math的靜態函式, 所以不需實體化Math 物件, 只要直接呼叫 Math.floor()就能使用。

+ +

(此外Math 並不是建構子).

+ +

範例

+ +

使用 Math.floor()

+ +
Math.floor( 45.95); //  45
+Math.floor( 45.05); //  45
+Math.floor(  4   ); //   4
+Math.floor(-45.05); // -46
+Math.floor(-45.95); // -46
+
+ +

Decimal adjustment

+ +
// Closure
+(function() {
+  /**
+   * Decimal adjustment of a number.
+   *
+   * @param {String}  type  The type of adjustment.
+   * @param {Number}  value The number.
+   * @param {Integer} exp   The exponent (the 10 logarithm of the adjustment base).
+   * @returns {Number} The adjusted value.
+   */
+  function decimalAdjust(type, value, exp) {
+    // If the exp is undefined or zero...
+    if (typeof exp === 'undefined' || +exp === 0) {
+      return Math[type](value);
+    }
+    value = +value;
+    exp = +exp;
+    // If the value is not a number or the exp is not an integer...
+    if (isNaN(value) || !(typeof exp === 'number' && exp % 1 === 0)) {
+      return NaN;
+    }
+    // Shift
+    value = value.toString().split('e');
+    value = Math[type](+(value[0] + 'e' + (value[1] ? (+value[1] - exp) : -exp)));
+    // Shift back
+    value = value.toString().split('e');
+    return +(value[0] + 'e' + (value[1] ? (+value[1] + exp) : exp));
+  }
+
+  // Decimal round
+  if (!Math.round10) {
+    Math.round10 = function(value, exp) {
+      return decimalAdjust('round', value, exp);
+    };
+  }
+  // Decimal floor
+  if (!Math.floor10) {
+    Math.floor10 = function(value, exp) {
+      return decimalAdjust('floor', value, exp);
+    };
+  }
+  // Decimal ceil
+  if (!Math.ceil10) {
+    Math.ceil10 = function(value, exp) {
+      return decimalAdjust('ceil', value, exp);
+    };
+  }
+})();
+
+// Round
+Math.round10(55.55, -1);   // 55.6
+Math.round10(55.549, -1);  // 55.5
+Math.round10(55, 1);       // 60
+Math.round10(54.9, 1);     // 50
+Math.round10(-55.55, -1);  // -55.5
+Math.round10(-55.551, -1); // -55.6
+Math.round10(-55, 1);      // -50
+Math.round10(-55.1, 1);    // -60
+// Floor
+Math.floor10(55.59, -1);   // 55.5
+Math.floor10(59, 1);       // 50
+Math.floor10(-55.51, -1);  // -55.6
+Math.floor10(-51, 1);      // -60
+// Ceil
+Math.ceil10(55.51, -1);    // 55.6
+Math.ceil10(51, 1);        // 60
+Math.ceil10(-55.59, -1);   // -55.5
+Math.ceil10(-59, 1);       // -50
+
+ +

規範

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
SpecificationStatusComment
{{SpecName('ES1')}}{{Spec2('ES1')}}Initial definition. Implemented in JavaScript 1.0.
{{SpecName('ES5.1', '#sec-15.8.2.9', 'Math.floor')}}{{Spec2('ES5.1')}}
{{SpecName('ES6', '#sec-math.floor', 'Math.floor')}}{{Spec2('ES6')}}
{{SpecName('ESDraft', '#sec-math.floor', 'Math.floor')}}{{Spec2('ESDraft')}}
+ +

瀏覽器相容性

+ + + +

{{Compat("javascript.builtins.Math.floor")}}

+ +

參見

+ + diff --git a/files/zh-tw/web/javascript/reference/global_objects/math/index.html b/files/zh-tw/web/javascript/reference/global_objects/math/index.html new file mode 100644 index 0000000000..c67999150e --- /dev/null +++ b/files/zh-tw/web/javascript/reference/global_objects/math/index.html @@ -0,0 +1,196 @@ +--- +title: Math +slug: Web/JavaScript/Reference/Global_Objects/Math +tags: + - JavaScript + - Math + - NeedsTranslation + - Reference + - TopicStub +translation_of: Web/JavaScript/Reference/Global_Objects/Math +--- +
{{JSRef}}
+ +

Math 是一個擁有數學常數及數學函數（非函式物件）屬性及方法的內建物件。

+ +

描述

+ +

不像其他的全域物件，Math 並非建構函式。所有 Math 的屬性及方法皆為靜態。你可以使用 Math.PI 來參考到圓周率 pi 的常數值，以及可以呼叫 Math.sin(x) 函式來計算三角函數正弦曲線 sine（x 為方法的引數）。常數是由 JavaScript 中實數的完整精度來定義。

+ +

屬性

+ +
+
{{jsxref("Math.E")}}
+
歐拉常數 (此指自然常數) ，也是自然對數的底數，約為2.718。
+
{{jsxref("Math.LN2")}}
+
2 的自然對數，約為0.693。
+
{{jsxref("Math.LN10")}}
+
10 的自然對數，約為2.303。
+
{{jsxref("Math.LOG2E")}}
+
以 2 為底的 E 的對數，約為1.443。
+
{{jsxref("Math.LOG10E")}}
+
以 10 為底的 E 的對數，約為0.434。
+
{{jsxref("Math.PI")}}
+
一個圓的圓周和其直徑比值，約為 3.14159。
+
{{jsxref("Math.SQRT1_2")}}
+
1/2的平方根；也就是1除以2的平方根，約為 0.707。
+
{{jsxref("Math.SQRT2")}}
+
2的平方根，約為 1.414。
+
+ +

方法

+ +
+

注意三角函數 (sin(), cos(), tan(), asin(), acos(), atan(), atan2()) 的參數或回傳值的角度皆以弧度為單位。把角度乘上 (Math.PI / 180) 會得到弧度單位，將弧度除以該數則會轉換回一般所用的角度單位。

+
+ +
+

注意許多數學方法的精度是取決於實作方式的。這意味著不同的瀏覽器可能會得到不同的結果，甚至同一個 JS引擎在不同的作業系統或架構上所得到的結果都有可能相異。

+
+ +
+
{{jsxref("Global_Objects/Math/abs", "Math.abs(x)")}}
+
回傳 x 的絕對值。
+
{{jsxref("Global_Objects/Math/acos", "Math.acos(x)")}}
+
回傳 x 的反餘弦值。
+
{{jsxref("Global_Objects/Math/acosh", "Math.acosh(x)")}}
+
Returns the hyperbolic arccosine of a number.
+
{{jsxref("Global_Objects/Math/asin", "Math.asin(x)")}}
+
回傳 x 的反正弦值。
+
{{jsxref("Global_Objects/Math/asinh", "Math.asinh(x)")}}
+
Returns the hyperbolic arcsine of a number.
+
{{jsxref("Global_Objects/Math/atan", "Math.atan(x)")}}
+
回傳 x 的反正切值。
+
{{jsxref("Global_Objects/Math/atanh", "Math.atanh(x)")}}
+
Returns the hyperbolic arctangent of a number.
+
{{jsxref("Global_Objects/Math/atan2", "Math.atan2(y, x)")}}
+
Returns the arctangent of the quotient of its arguments.
+
{{jsxref("Global_Objects/Math/cbrt", "Math.cbrt(x)")}}
+
回傳 x 的立方根值。
+
{{jsxref("Global_Objects/Math/ceil", "Math.ceil(x)")}}
+
回傳不小於 x 的最小整數值。
+
{{jsxref("Global_Objects/Math/clz32", "Math.clz32(x)")}}
+
Returns the number of leading zeroes of a 32-bit integer.
+
{{jsxref("Global_Objects/Math/cos", "Math.cos(x)")}}
+
回傳 x 的餘弦值。
+
{{jsxref("Global_Objects/Math/cosh", "Math.cosh(x)")}}
+
Returns the hyperbolic cosine of a number.
+
{{jsxref("Global_Objects/Math/exp", "Math.exp(x)")}}
+
回傳 Ex，x 為給定數值，E 為歐拉常數 (自然對數的底數)。
+
{{jsxref("Global_Objects/Math/expm1", "Math.expm1(x)")}}
+
回傳 exp(x) 減去1的值。
+
{{jsxref("Global_Objects/Math/floor", "Math.floor(x)")}}
+
回傳不大於 x 的最大整數值。
+
{{jsxref("Global_Objects/Math/fround", "Math.fround(x)")}}
+
Returns the nearest single precision float representation of a number.
+
{{jsxref("Global_Objects/Math/hypot", "Math.hypot([x[, y[, …]]])")}}
+
回傳參數平方之和的平方根。
+
{{jsxref("Global_Objects/Math/imul", "Math.imul(x, y)")}}
+
Returns the result of a 32-bit integer multiplication.
+
{{jsxref("Global_Objects/Math/log", "Math.log(x)")}}
+
回傳 x 的自然對數值。
+
{{jsxref("Global_Objects/Math/log1p", "Math.log1p(x)")}}
+
回傳 1 + x 的自然對數值。
+
{{jsxref("Global_Objects/Math/log10", "Math.log10(x)")}}
+
回傳以 10 為底，x 的對數值。
+
{{jsxref("Global_Objects/Math/log2", "Math.log2(x)")}}
+
回傳以 2 為底，x 的對數值。
+
{{jsxref("Global_Objects/Math/max", "Math.max([x[, y[, …]]])")}}
+
回傳給定數值中的最大值。
+
{{jsxref("Global_Objects/Math/min", "Math.min([x[, y[, …]]])")}}
+
回傳給定數值中的最小值。
+
{{jsxref("Global_Objects/Math/pow", "Math.pow(x, y)")}}
+
回傳 x 的 y 次方，也就是 xy。
+
{{jsxref("Global_Objects/Math/random", "Math.random()")}}
+
回傳一個 0 到 1 之間的偽隨機值。
+
{{jsxref("Global_Objects/Math/round", "Math.round(x)")}}
+
回傳 x 的四捨五入值。
+
{{jsxref("Global_Objects/Math/sign", "Math.sign(x)")}}
+
回傳 x 的正負號，也就是回傳 x 的正負。
+
{{jsxref("Global_Objects/Math/sin", "Math.sin(x)")}}
+
回傳 x 的正弦值。
+
{{jsxref("Global_Objects/Math/sinh", "Math.sinh(x)")}}
+
Returns the hyperbolic sine of a number.
+
{{jsxref("Global_Objects/Math/sqrt", "Math.sqrt(x)")}}
+
回傳 x 的正平方根。
+
{{jsxref("Global_Objects/Math/tan", "Math.tan(x)")}}
+
回傳 x 的正切值。
+
{{jsxref("Global_Objects/Math/tanh", "Math.tanh(x)")}}
+
Returns the hyperbolic tangent of a number.
+
Math.toSource() {{non-standard_inline}}
+
回傳字串 "Math"。
+
{{jsxref("Global_Objects/Math/trunc", "Math.trunc(x)")}}
+
Returns the integral part of the number x, removing any fractional digits.
+
+ +

擴充 Math 物件

+ +

As most of the built-in objects in JavaScript, the Math object can be extended with custom properties and methods. To extend the Math object, you do not use 'prototype'. Instead, you directly extend Math:

+ +
Math.propName = propValue;
+Math.methodName = methodRef;
+ +

For instance, the following example adds a method to the Math object for calculating the greatest common divisor of a list of arguments.

+ +
/* Variadic function -- Returns the greatest common divisor of a list of arguments */
+Math.gcd = function() {
+    if (arguments.length == 2) {
+        if (arguments[1] == 0)
+            return arguments[0];
+        else
+            return Math.gcd(arguments[1], arguments[0] % arguments[1]);
+    } else if (arguments.length > 2) {
+        var result = Math.gcd(arguments[0], arguments[1]);
+        for (var i = 2; i < arguments.length; i++)
+            result = Math.gcd(result, arguments[i]);
+        return result;
+    }
+};
+ +

Try it:

+ +
console.log(Math.gcd(20, 30, 15, 70, 40)); // `5`
+ +

規範

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
SpecificationStatusComment
{{SpecName('ES1')}}{{Spec2('ES1')}}Initial definition. Implemented in JavaScript 1.1.
{{SpecName('ES5.1', '#sec-15.8', 'Math')}}{{Spec2('ES5.1')}} 
{{SpecName('ES6', '#sec-math-object', 'Math')}}{{Spec2('ES6')}}New methods {{jsxref("Math.log10()", "log10()")}}, {{jsxref("Math.log2()", "log2()")}}, {{jsxref("Math.log1p()", "log1p()")}}, {{jsxref("Math.expm1()", "expm1()")}}, {{jsxref("Math.cosh()", "cosh()")}}, {{jsxref("Math.sinh()", "sinh()")}}, {{jsxref("Math.tanh()", "tanh()")}}, {{jsxref("Math.acosh()", "acosh()")}}, {{jsxref("Math.asinh()", "asinh()")}}, {{jsxref("Math.atanh()", "atanh()")}}, {{jsxref("Math.hypot()", "hypot()")}}, {{jsxref("Math.trunc()", "trunc()")}}, {{jsxref("Math.sign()", "sign()")}}, {{jsxref("Math.imul()", "imul()")}}, {{jsxref("Math.fround()", "fround()")}}, {{jsxref("Math.cbrt()", "cbrt()")}} and {{jsxref("Math.clz32()", "clz32()")}} added.
{{SpecName('ESDraft', '#sec-math-object', 'Math')}}{{Spec2('ESDraft')}} 
+ +

瀏覽器相容性

+ + + +

{{Compat("javascript.builtins.Math")}}

+ +

參見

+ + diff --git a/files/zh-tw/web/javascript/reference/global_objects/math/max/index.html b/files/zh-tw/web/javascript/reference/global_objects/math/max/index.html new file mode 100644 index 0000000000..1f53898090 --- /dev/null +++ b/files/zh-tw/web/javascript/reference/global_objects/math/max/index.html @@ -0,0 +1,117 @@ +--- +title: Math.max() +slug: Web/JavaScript/Reference/Global_Objects/Math/max +tags: + - JavaScript + - Math + - Method + - Reference +translation_of: Web/JavaScript/Reference/Global_Objects/Math/max +--- +
{{JSRef}}
+ +

Math.max() 函式會回傳零或多個數字中的最大值。

+ +
{{EmbedInteractiveExample("pages/js/math-max.html")}}
+ + + +

語法

+ +
Math.max([value1[, value2[, ...]]])
+ +

Parameters

+ +
+
value1, value2, ...
+
Numbers.
+
+ +

Return value

+ +

The largest of the given numbers. If at least one of the arguments cannot be converted to a number, {{jsxref("NaN")}} is returned.

+ +

說明

+ +

Because max() is a static method of Math, you always use it as Math.max(), rather than as a method of a Math object you created (Math is not a constructor).

+ +

If no arguments are given, the result is -{{jsxref("Infinity")}}.

+ +

If at least one of arguments cannot be converted to a number, the result is {{jsxref("NaN")}}.

+ +

範例

+ +

Using Math.max()

+ +
Math.max(10, 20);   //  20
+Math.max(-10, -20); // -10
+Math.max(-10, 20);  //  20
+
+ +

Getting the maximum element of an array

+ +

{{jsxref("Array.prototype.reduce", "Array.reduce()")}} can be used to find the maximum element in a numeric array, by comparing each value:

+ +
var arr = [1,2,3];
+var max = arr.reduce(function(a, b) {
+    return Math.max(a, b);
+});
+
+ +

The following function uses {{jsxref("Function.prototype.apply()")}} to get the maximum of an array. getMaxOfArray([1, 2, 3]) is equivalent to Math.max(1, 2, 3), but you can use getMaxOfArray() on programmatically constructed arrays. This should only be used for arrays with relatively few elements.

+ +
function getMaxOfArray(numArray) {
+  return Math.max.apply(null, numArray);
+}
+ +

The new spread operator is a shorter way of writing the apply solution to get the maximum of an array:

+ +
var arr = [1, 2, 3];
+var max = Math.max(...arr);
+
+ +

However, both spread (...) and apply will either fail or return the wrong result if the array has too many elements, because they try to pass the array elements as function parameters. See Using apply and built-in functions for more details. The reduce solution does not have this problem.

+ +

規範

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
SpecificationStatusComment
{{SpecName('ES1')}}{{Spec2('ES1')}}Initial definition. Implemented in JavaScript 1.0.
{{SpecName('ES5.1', '#sec-15.8.2.11', 'Math.max')}}{{Spec2('ES5.1')}} 
{{SpecName('ES6', '#sec-math.max', 'Math.max')}}{{Spec2('ES6')}} 
{{SpecName('ESDraft', '#sec-math.max', 'Math.max')}}{{Spec2('ESDraft')}} 
+ +

瀏覽器相容性

+ + + +

{{Compat("javascript.builtins.Math.max")}}

+ +

參見

+ + diff --git a/files/zh-tw/web/javascript/reference/global_objects/math/pow/index.html b/files/zh-tw/web/javascript/reference/global_objects/math/pow/index.html new file mode 100644 index 0000000000..00ccb041ae --- /dev/null +++ b/files/zh-tw/web/javascript/reference/global_objects/math/pow/index.html @@ -0,0 +1,107 @@ +--- +title: Math.pow() +slug: Web/JavaScript/Reference/Global_Objects/Math/pow +tags: + - 次方 +translation_of: Web/JavaScript/Reference/Global_Objects/Math/pow +--- +
{{JSRef}}
+ +

Math.pow() 函式回傳 base 的 exponent 次方（幂）值，也就是 baseexponent。

+ +

語法

+ +
Math.pow(base, exponent)
+ +

參數

+ +
+
base
+
基數。
+
exponent
+
要乘上 base 幾次的指數。
+
+ +

回傳值

+ +

A number representing the given base taken to the power of the given exponent.

+ +

敘述

+ +

The Math.pow() function returns the base to the exponent power, that is, baseexponent, the base and the exponent are in decimal numeral system.

+ +

由於 pow() 是 Math 的靜態方法，you always use it as Math.pow(), rather than as a method of a Math object you created（Math 並沒有建構子）。

+ +

示例

+ +

使用 Math.pow()

+ +
// simple
+Math.pow(7, 2);    // 49
+Math.pow(7, 3);    // 343
+Math.pow(2, 10);   // 1024
+// fractional exponents
+Math.pow(4, 0.5);  // 2 （4 的平方根）
+Math.pow(8, 1/3);  // 2 （8 的立方根）
+Math.pow(2, 0.5);  // 1.4142135623730951 （2 的平方根）
+Math.pow(2, 1/3);  // 1.2599210498948732 （2 的立方根）
+// signed exponents
+Math.pow(7, -2);   // 0.02040816326530612 (1/49)
+Math.pow(8, -1/3); // 0.5
+// signed bases
+Math.pow(-7, 2);   // 49 (負負得正，2次方都是正數)
+Math.pow(-7, 3);   // -343 (3次方有可能為負數)
+Math.pow(-7, 0.5); // NaN (負數沒辦法得出一個實數平方根)
+// due to "even" and "odd" roots laying close to each other,
+// and limits in the floating number precision,
+// negative bases with fractional exponents always return NaN
+Math.pow(-7, 1/3); // NaN
+
+ +

規範

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
規範狀態註解
{{SpecName('ES1')}}{{Spec2('ES1')}}Initial definition. Implemented in JavaScript 1.0.
{{SpecName('ES5.1', '#sec-15.8.2.13', 'Math.pow')}}{{Spec2('ES5.1')}}
{{SpecName('ES6', '#sec-math.pow', 'Math.pow')}}{{Spec2('ES6')}}
{{SpecName('ESDraft', '#sec-math.pow', 'Math.pow')}}{{Spec2('ESDraft')}}
+ +

瀏覽器相容性

+ + + +

{{Compat("javascript.builtins.Math.pow")}}

+ +

參見

+ + diff --git a/files/zh-tw/web/javascript/reference/global_objects/math/random/index.html b/files/zh-tw/web/javascript/reference/global_objects/math/random/index.html new file mode 100644 index 0000000000..4f7b65f844 --- /dev/null +++ b/files/zh-tw/web/javascript/reference/global_objects/math/random/index.html @@ -0,0 +1,95 @@ +--- +title: Math.random() +slug: Web/JavaScript/Reference/Global_Objects/Math/random +tags: + - 浮點數 + - 隨機 +translation_of: Web/JavaScript/Reference/Global_Objects/Math/random +--- +
{{JSRef}}
+ +

函數 Math.random() 會回傳一個偽隨機小數 (pseudo-random) 介於0到1之間(包含 0，不包含1) ，大致符合數學與統計上的均勻分佈 (uniform distribution) ，您可以選定想要的數字區間，它會透過演算法被產生並且不允許使用者自行跳選或重設成特定數字。{{EmbedInteractiveExample("pages/js/math-random.html")}}

+ +
+

Math.random() 所產生的偽隨機小數不符合加密學安全性要求。請勿使用於任何加密、資安相關領域。

+ +

如有加密需求建議參考Web Crypto APIwindow.crypto.getRandomValues()

+
+ +

語法

+ +
Math.random()
+ +

回傳值 Return value

+ +

回傳一個偽隨機小數 (pseudo-random)，小數也稱浮點數； 介於0到1之間(包含 0，不包含1) 。

+ +

範例

+ +

請留意JavaScript中的數字與許多語言一樣使用 IEEE 754 floating point numbers with round-to-nearest-even behavior, the ranges claimed for the functions below (excluding the one for Math.random() itself) aren't exact. If extremely large bounds are chosen (253 or higher), it's possible in extremely rare cases to calculate the usually-excluded upper bound.

+ +

Getting a random number between 0 (inclusive) and 1 (exclusive)

+ +
function getRandom() {
+  return Math.random();
+}
+
+ +

Getting a random number between two values

+ +

This example returns a random number between the specified values. The returned value is no lower than (and may possibly equal) min, and is less than (and not equal) max.

+ +
function getRandomArbitrary(min, max) {
+  return Math.random() * (max - min) + min;
+}
+
+ +

Getting a random integer between two values

+ +

This example returns a random integer between the specified values. The value is no lower than min (or the next integer greater than min if min isn't an integer), and is less than (but not equal to) max.

+ +
function getRandomInt(min, max) {
+  min = Math.ceil(min);
+  max = Math.floor(max);
+  return Math.floor(Math.random() * (max - min) + min); //The maximum is exclusive and the minimum is inclusive
+}
+
+ +
+

It might be tempting to use Math.round() to accomplish that, but doing so would cause your random numbers to follow a non-uniform distribution, which may not be acceptable for your needs.

+
+ +

Getting a random integer between two values, inclusive

+ +

While the getRandomInt() function above is inclusive at the minimum, it's exclusive at the maximum. What if you need the results to be inclusive at both the minimum and the maximum? The getRandomIntInclusive() function below accomplishes that.

+ +
function getRandomIntInclusive(min, max) {
+  min = Math.ceil(min);
+  max = Math.floor(max);
+  return Math.floor(Math.random() * (max - min + 1) + min); //The maximum is inclusive and the minimum is inclusive
+}
+ +

Specifications

+ + + + + + + + + + +
Specification
{{SpecName('ESDraft', '#sec-math.random', 'Math.random')}}
+ +

瀏覽器相容性

+ + + +

{{Compat("javascript.builtins.Math.random")}}

+ +

其他參考資料

+ + diff --git a/files/zh-tw/web/javascript/reference/global_objects/math/round/index.html b/files/zh-tw/web/javascript/reference/global_objects/math/round/index.html new file mode 100644 index 0000000000..5e6a0ea694 --- /dev/null +++ b/files/zh-tw/web/javascript/reference/global_objects/math/round/index.html @@ -0,0 +1,212 @@ +--- +title: Math.round() +slug: Web/JavaScript/Reference/Global_Objects/Math/round +tags: + - JavaScript + - Math + - Method + - Reference +translation_of: Web/JavaScript/Reference/Global_Objects/Math/round +--- +
{{JSRef}}
+ +

Math.round() 函數回傳四捨五入後的近似值.

+ +

表達式

+ +
Math.round(x)
+ +

參數

+ +
+
x
+
數字.
+
+ +

描述

+ +

如果小數位的部分值大於 0.5, 這個值將會進位. 如果小數位的部分值小於 0.5, 這個值將不會進位.

+ +

由於 round() 是靜態的方法, 所以總是得這樣使用 Math.round(), 而非作為 Math 物件的一個方法 (Math並沒有建構子).

+ +

範例

+ +

使用 Math.round()

+ +
// Returns the value 20
+x = Math.round(20.49);
+
+// Returns the value 21
+x = Math.round(20.5);
+
+// Returns the value -20
+x = Math.round(-20.5);
+
+// Returns the value -21
+x = Math.round(-20.51);
+
+// Returns the value 1 (!)
+// Note the rounding error because of inaccurate floating point arithmetics
+// Compare this with Math.round10(1.005, -2) from the example below
+x = Math.round(1.005*100)/100;
+
+ +

十進位近似值

+ +
// 閉包含數
+(function() {
+  /**
+   * Decimal adjustment of a number.
+   *
+   * @param {String}  type  The type of adjustment.
+   * @param {Number}  value The number.
+   * @param {Integer} exp   The exponent (the 10 logarithm of the adjustment base).
+   * @returns {Number} The adjusted value.
+   */
+  function decimalAdjust(type, value, exp) {
+    // If the exp is undefined or zero...
+    if (typeof exp === 'undefined' || +exp === 0) {
+      return Math[type](value);
+    }
+    value = +value;
+    exp = +exp;
+    // If the value is not a number or the exp is not an integer...
+    if (isNaN(value) || !(typeof exp === 'number' && exp % 1 === 0)) {
+      return NaN;
+    }
+    // Shift
+    value = value.toString().split('e');
+    value = Math[type](+(value[0] + 'e' + (value[1] ? (+value[1] - exp) : -exp)));
+    // Shift back
+    value = value.toString().split('e');
+    return +(value[0] + 'e' + (value[1] ? (+value[1] + exp) : exp));
+  }
+
+  // Decimal round
+  if (!Math.round10) {
+    Math.round10 = function(value, exp) {
+      return decimalAdjust('round', value, exp);
+    };
+  }
+  // Decimal floor
+  if (!Math.floor10) {
+    Math.floor10 = function(value, exp) {
+      return decimalAdjust('floor', value, exp);
+    };
+  }
+  // Decimal ceil
+  if (!Math.ceil10) {
+    Math.ceil10 = function(value, exp) {
+      return decimalAdjust('ceil', value, exp);
+    };
+  }
+})();
+
+// Round
+Math.round10(55.55, -1);   // 55.6
+Math.round10(55.549, -1);  // 55.5
+Math.round10(55, 1);       // 60
+Math.round10(54.9, 1);     // 50
+Math.round10(-55.55, -1);  // -55.5
+Math.round10(-55.551, -1); // -55.6
+Math.round10(-55, 1);      // -50
+Math.round10(-55.1, 1);    // -60
+Math.round10(1.005, -2);   // 1.01 -- compare this with Math.round(1.005*100)/100 above
+// Floor
+Math.floor10(55.59, -1);   // 55.5
+Math.floor10(59, 1);       // 50
+Math.floor10(-55.51, -1);  // -55.6
+Math.floor10(-51, 1);      // -60
+// Ceil
+Math.ceil10(55.51, -1);    // 55.6
+Math.ceil10(51, 1);        // 60
+Math.ceil10(-55.59, -1);   // -55.5
+Math.ceil10(-59, 1);       // -50
+
+ +

規範

+ + + + + + + + + + + + + + + + + + + + + + + + +
規範狀態註
{{SpecName('ES1')}}{{Spec2('ES1')}}Initial definition. Implemented in JavaScript 1.0.
{{SpecName('ES5.1', '#sec-15.8.2.15', 'Math.round')}}{{Spec2('ES5.1')}} 
{{SpecName('ES6', '#sec-math.round', 'Math.round')}}{{Spec2('ES6')}} 
+ +

瀏覽器相容性

+ +
{{CompatibilityTable}}
+ +
+ + + + + + + + + + + + + + + + + + + +
FeatureChromeFirefox (Gecko)Internet ExplorerOperaSafari (WebKit)
Basic support{{CompatVersionUnknown}}{{CompatVersionUnknown}}{{CompatVersionUnknown}}{{CompatVersionUnknown}}{{CompatVersionUnknown}}
+
+ +
+ + + + + + + + + + + + + + + + + + + +
FeatureAndroidFirefox Mobile (Gecko)IE PhoneOpera MobileSafari Mobile
Basic support{{CompatVersionUnknown}}{{CompatVersionUnknown}}{{CompatVersionUnknown}}{{CompatVersionUnknown}}{{CompatVersionUnknown}}
+
+ +

參見

+ + -- cgit v1.2.3-54-g00ecf