From 218934fa2ed1c702a6d3923d2aa2cc6b43c48684 Mon Sep 17 00:00:00 2001 From: Peter Bengtsson Date: Tue, 8 Dec 2020 14:43:23 -0500 Subject: initial commit --- .../global_objects/number/toexponential/index.html | 164 +++++++++++++++++++++ 1 file changed, 164 insertions(+) create mode 100644 files/zh-tw/web/javascript/reference/global_objects/number/toexponential/index.html (limited to 'files/zh-tw/web/javascript/reference/global_objects/number/toexponential') diff --git a/files/zh-tw/web/javascript/reference/global_objects/number/toexponential/index.html b/files/zh-tw/web/javascript/reference/global_objects/number/toexponential/index.html new file mode 100644 index 0000000000..622314ecfb --- /dev/null +++ b/files/zh-tw/web/javascript/reference/global_objects/number/toexponential/index.html @@ -0,0 +1,164 @@ +--- +title: Number.prototype.toExponential() +slug: Web/JavaScript/Reference/Global_Objects/Number/toExponential +tags: + - 數字 + - 科學技數法 +translation_of: Web/JavaScript/Reference/Global_Objects/Number/toExponential +--- +
{{JSRef}}
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toExponential() method 用來將數字轉成「科學記數法」格式。

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語法

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numObj.toExponential([fractionDigits])
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參數

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參數可選默認值類型說明
fractionDigits●默認盡可能將數字完整顯示{{jsxref("Number")}}（正整數）小數點後的位數。需為 0 至 20 之間。
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回傳直

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一 string，將數字以「科學計數法」格式表示出來

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Exceptions

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{{jsxref("RangeError")}}
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若 fractionDigits 超出範圍（可接受的範圍是 0 ～ 20 之間的正整數）觸發 {{jsxref("RangeError")}}。
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{{jsxref("TypeError")}}
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若參數 fractionDigits 不是 {{jsxref("Number")}}，則觸發{{jsxref("TypeError")}}。
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Description

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If the fractionDigits argument is omitted, the number of digits after the decimal point defaults to the number of digits necessary to represent the value uniquely.

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If you use the toExponential() method for a numeric literal and the numeric literal has no exponent and no decimal point, leave whitespace(s) before the dot that precedes the method call to prevent the dot from being interpreted as a decimal point.

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If a number has more digits than requested by the fractionDigits parameter, the number is rounded to the nearest number represented by fractionDigits digits. See the discussion of rounding in the description of the {{jsxref("Number.prototype.toFixed", "toFixed()")}} method, which also applies to toExponential().

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範例

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Using toExponential

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var numObj = 77.1234;
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+console.log(numObj.toExponential());  // logs 7.71234e+1
+console.log(numObj.toExponential(4)); // logs 7.7123e+1
+console.log(numObj.toExponential(2)); // logs 7.71e+1
+console.log(77.1234.toExponential()); // logs 7.71234e+1
+console.log(77 .toExponential());     // logs 7.7e+1
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Specifications

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SpecificationStatusComment
{{SpecName('ES3')}}{{Spec2('ES3')}}Initial definition. Implemented in JavaScript 1.5.
{{SpecName('ES5.1', '#sec-15.7.4.6', 'Number.prototype.toExponential')}}{{Spec2('ES5.1')}} 
{{SpecName('ES6', '#sec-number.prototype.toexponential', 'Number.prototype.toExponential')}}{{Spec2('ES6')}} 
{{SpecName('ESDraft', '#sec-number.prototype.toexponential', 'Number.prototype.toExponential')}}{{Spec2('ESDraft')}} 
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瀏覽器支援度

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{{CompatibilityTable}}
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FeatureChromeFirefox (Gecko)Internet ExplorerOperaSafari
Basic support{{CompatVersionUnknown}}{{CompatVersionUnknown}}{{CompatVersionUnknown}}{{CompatVersionUnknown}}{{CompatVersionUnknown}}
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FeatureAndroidChrome for AndroidFirefox Mobile (Gecko)IE MobileOpera MobileSafari Mobile
Basic support{{CompatVersionUnknown}}{{CompatVersionUnknown}}{{CompatVersionUnknown}}{{CompatVersionUnknown}}{{CompatVersionUnknown}}{{CompatVersionUnknown}}
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延伸閱讀

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