构造Blob时的字符串编码 [英] String encoding when constructing a Blob

问题描述

我知道JavaScript字符串通常编码为具有每个字符至少两个字节的编码（UTF-16或UCS-2）。

I know that JavaScript strings are usually encoded with an encoding taking at least two bytes per character (UTF-16 or UCS-2).

但是，当构造Blob时，似乎使用了不同的编码，因为当我将它读为 ArrayBuffer 时，返回的缓冲区为3欧元符号。

However, when constructing a Blob, a different encoding appears to be used because when I read it as ArrayBuffer, the length of the returned buffer is 3 for an Euro sign.

var b = new Blob(['€']);

推荐答案

根据 W3C ，它是 UTF-8 编码。

演示：

// Create a Blob with an Euro-char (U+20AC)
var b = new Blob(['€']);
var fr = new FileReader();

fr.onload = function() {
  ua = new Uint8Array(fr.result);
  // This will log "3|226|130|172"
  //                  E2  82  AC
  // In UTF-16, it would be only 2 bytes long
  console.log(
    fr.result.byteLength + '|' + 
    ua[0]  + '|' + 
    ua[1] + '|' + 
    ua[2] + ''
  );
};
fr.readAsArrayBuffer(b);

在 JSFiddle

Play with that on JSFiddle.

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