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/dataview/index.html | 173 +++++++++++++++++++++ 1 file changed, 173 insertions(+) create mode 100644 files/zh-tw/web/javascript/reference/global_objects/dataview/index.html (limited to 'files/zh-tw/web/javascript/reference/global_objects/dataview') diff --git a/files/zh-tw/web/javascript/reference/global_objects/dataview/index.html b/files/zh-tw/web/javascript/reference/global_objects/dataview/index.html new file mode 100644 index 0000000000..d7cf6d6ed4 --- /dev/null +++ b/files/zh-tw/web/javascript/reference/global_objects/dataview/index.html @@ -0,0 +1,173 @@ +--- +title: DataView +slug: Web/JavaScript/Reference/Global_Objects/DataView +translation_of: Web/JavaScript/Reference/Global_Objects/DataView +--- +
{{JSRef}}
+ +

DataView 視圖提供了一個底層介面來讀寫 {{jsxref("ArrayBuffer")}} 中的二進位資料。DataView 能用多種不同的型別對 ArrayBuffer 進行修改、解讀，且可自訂資料的位元組順序而不受系統平台限制。DataView 物件僅為視圖，並不會存放資料，所有的資料皆實際儲存於 ArrayBuffer 物件當中。

+ +

語法

+ +
new DataView(buffer [, byteOffset [, byteLength]])
+ +

參數

+ +
+
buffer
+
要給DataView物件操作的資料容器並且不能為null
+
byteOffset {{optional_inline}}
+
The offset, in bytes, to the first byte in the specified buffer for the new view to reference. If not specified, the view of the buffer will start with the first byte.
+
byteLength {{optional_inline}}
+
The number of elements in the byte array. If unspecified, length of the view will match the buffer's length.
+
+ +

回傳值

+ +

A new DataView object representing the specified data buffer.

+ +

Errors thrown

+ +
+
{{jsxref("RangeError")}}
+
Thrown if the byteOffset and byteLength result in the specified view extending past the end of the buffer.
+
+ +

描述

+ +

位元組順序

+ +

Multi-byte number formats are represented in memory differently depending on machine architecture, see {{Glossary("Endianness")}} for an explanation. DataView accessors provide explicit control of how data will be accessed irrespective of the platform architecture's endianness.

+ +
var littleEndian = (function() {
+  var buffer = new ArrayBuffer(2);
+  new DataView(buffer).setInt16(0, 256, true /* littleEndian */);
+  // Int16Array uses the platform's endianness.
+  return new Int16Array(buffer)[0] === 256;
+})();
+console.log(littleEndian); // true or false
+
+ +

屬性

+ +
+
DataView.length
+
The DataView constructor's length property whose value is 3.
+
{{jsxref("DataView.prototype")}}
+
Allows the addition of properties to all DataView objects.
+
+ +

DataView 實例

+ +

All DataView instances inherit from {{jsxref("DataView.prototype")}}.

+ +

屬性

+ +

{{page('en-US/Web/JavaScript/Reference/Global_Objects/DataView/prototype','Properties')}}

+ +

方法

+ +

{{page('en-US/Web/JavaScript/Reference/Global_Objects/DataView/prototype','Methods')}}

+ +

範例

+ +
var buffer = new ArrayBuffer(16);
+var dv = new DataView(buffer, 0);
+
+dv.setInt16(1, 42);
+dv.getInt16(1); //42
+
+ +

規範

+ + + + + + + + + + + + + + + + + + + + + + + + +
SpecificationStatusComment
{{SpecName('Typed Array')}}{{Spec2('Typed Array')}}Superseded by ECMAScript 6
{{SpecName('ES6', '#sec-dataview-constructor', 'DataView')}}{{Spec2('ES6')}}Initial definition in an ECMA standard
{{SpecName('ESDraft', '#sec-dataview-constructor', 'DataView')}}{{Spec2('ESDraft')}} 
+ +

瀏覽器相容性

+ +

{{CompatibilityTable}}

+ +
+ + + + + + + + + + + + + + + + + + + +
FeatureChromeFirefox (Gecko)Internet ExplorerOperaSafari
Basic support9.0{{CompatGeckoDesktop("15.0")}}1012.15.1
+
+ +
+ + + + + + + + + + + + + + + + + + + + + +
FeatureAndroidChrome for AndroidFirefox Mobile (Gecko)IE MobileOpera MobileSafari Mobile
Basic support4.0{{CompatVersionUnknown}}{{CompatGeckoMobile("15")}}{{CompatUnknown}}12.04.2
+
+ +

Firefox-specific notes

+ +

Starting with Gecko / SpiderMonkey 40 {{geckoRelease(40)}}, DataView requires to be constructed with a {{jsxref("Operators/new", "new")}} operator. Calling DataView() as a function without new, will throw a {{jsxref("TypeError")}} from now on.

+ +
var dv = DataView(buffer, 0);
+// TypeError: calling a builtin DataView constructor without new is forbidden
+ +
var dv = new DataView(buffer, 0);
+ +

參見

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