是否有一种普遍接受的技术可以有效地将JavaScript字符串转换为arraybuffer,反之亦然?具体来说,我希望能够将ArrayBuffer的内容写入localStorage,然后再将其读回来。


当前回答

尽管Dennis和gengkev使用Blob/FileReader的解决方案有效,但我不建议采用这种方法。这是一种解决简单问题的异步方法,比直接解决方案要慢得多。我在html5rocks上发布了一个更简单(更快)的解决方案: http://updates.html5rocks.com/2012/06/How-to-convert-ArrayBuffer-to-and-from-String

解决方案是:

function ab2str(buf) {
  return String.fromCharCode.apply(null, new Uint16Array(buf));
}

function str2ab(str) {
  var buf = new ArrayBuffer(str.length*2); // 2 bytes for each char
  var bufView = new Uint16Array(buf);
  for (var i=0, strLen=str.length; i<strLen; i++) {
    bufView[i] = str.charCodeAt(i);
  }
  return buf;
}

编辑:

Encoding API帮助解决字符串转换问题。请查看Jeff Posnik在Html5Rocks.com上对上述原创文章的回复。

摘录:

Encoding API使原始字节和原生JavaScript字符串之间的转换变得简单,而不考虑需要使用的许多标准编码中的哪一种。

<pre id="results"></pre>

<script>
  if ('TextDecoder' in window) {
    // The local files to be fetched, mapped to the encoding that they're using.
    var filesToEncoding = {
      'utf8.bin': 'utf-8',
      'utf16le.bin': 'utf-16le',
      'macintosh.bin': 'macintosh'
    };

    Object.keys(filesToEncoding).forEach(function(file) {
      fetchAndDecode(file, filesToEncoding[file]);
    });
  } else {
    document.querySelector('#results').textContent = 'Your browser does not support the Encoding API.'
  }

  // Use XHR to fetch `file` and interpret its contents as being encoded with `encoding`.
  function fetchAndDecode(file, encoding) {
    var xhr = new XMLHttpRequest();
    xhr.open('GET', file);
    // Using 'arraybuffer' as the responseType ensures that the raw data is returned,
    // rather than letting XMLHttpRequest decode the data first.
    xhr.responseType = 'arraybuffer';
    xhr.onload = function() {
      if (this.status == 200) {
        // The decode() method takes a DataView as a parameter, which is a wrapper on top of the ArrayBuffer.
        var dataView = new DataView(this.response);
        // The TextDecoder interface is documented at http://encoding.spec.whatwg.org/#interface-textdecoder
        var decoder = new TextDecoder(encoding);
        var decodedString = decoder.decode(dataView);
        // Add the decoded file's text to the <pre> element on the page.
        document.querySelector('#results').textContent += decodedString + '\n';
      } else {
        console.error('Error while requesting', file, this);
      }
    };
    xhr.send();
  }
</script>

其他回答

Blob比String.fromCharCode(null,array)慢得多;

但如果数组缓冲区太大,就会失败。我发现的最佳解决方案是使用String.fromCharCode(null,数组);并将其拆分为不会破坏堆栈的操作,但每次比单个char更快。

大数组缓冲区的最佳解决方案是:

function arrayBufferToString(buffer){

    var bufView = new Uint16Array(buffer);
    var length = bufView.length;
    var result = '';
    var addition = Math.pow(2,16)-1;

    for(var i = 0;i<length;i+=addition){

        if(i + addition > length){
            addition = length - i;
        }
        result += String.fromCharCode.apply(null, bufView.subarray(i,i+addition));
    }

    return result;

}

我发现这比使用blob快20倍。它也适用于超过100mb的大字符串。

请看这里:https://developer.mozilla.org/en-US/docs/Web/JavaScript/Typed_arrays/StringView (基于JavaScript ArrayBuffer接口的类似c语言的字符串接口)

尽管Dennis和gengkev使用Blob/FileReader的解决方案有效,但我不建议采用这种方法。这是一种解决简单问题的异步方法,比直接解决方案要慢得多。我在html5rocks上发布了一个更简单(更快)的解决方案: http://updates.html5rocks.com/2012/06/How-to-convert-ArrayBuffer-to-and-from-String

解决方案是:

function ab2str(buf) {
  return String.fromCharCode.apply(null, new Uint16Array(buf));
}

function str2ab(str) {
  var buf = new ArrayBuffer(str.length*2); // 2 bytes for each char
  var bufView = new Uint16Array(buf);
  for (var i=0, strLen=str.length; i<strLen; i++) {
    bufView[i] = str.charCodeAt(i);
  }
  return buf;
}

编辑:

Encoding API帮助解决字符串转换问题。请查看Jeff Posnik在Html5Rocks.com上对上述原创文章的回复。

摘录:

Encoding API使原始字节和原生JavaScript字符串之间的转换变得简单,而不考虑需要使用的许多标准编码中的哪一种。

<pre id="results"></pre>

<script>
  if ('TextDecoder' in window) {
    // The local files to be fetched, mapped to the encoding that they're using.
    var filesToEncoding = {
      'utf8.bin': 'utf-8',
      'utf16le.bin': 'utf-16le',
      'macintosh.bin': 'macintosh'
    };

    Object.keys(filesToEncoding).forEach(function(file) {
      fetchAndDecode(file, filesToEncoding[file]);
    });
  } else {
    document.querySelector('#results').textContent = 'Your browser does not support the Encoding API.'
  }

  // Use XHR to fetch `file` and interpret its contents as being encoded with `encoding`.
  function fetchAndDecode(file, encoding) {
    var xhr = new XMLHttpRequest();
    xhr.open('GET', file);
    // Using 'arraybuffer' as the responseType ensures that the raw data is returned,
    // rather than letting XMLHttpRequest decode the data first.
    xhr.responseType = 'arraybuffer';
    xhr.onload = function() {
      if (this.status == 200) {
        // The decode() method takes a DataView as a parameter, which is a wrapper on top of the ArrayBuffer.
        var dataView = new DataView(this.response);
        // The TextDecoder interface is documented at http://encoding.spec.whatwg.org/#interface-textdecoder
        var decoder = new TextDecoder(encoding);
        var decodedString = decoder.decode(dataView);
        // Add the decoded file's text to the <pre> element on the page.
        document.querySelector('#results').textContent += decodedString + '\n';
      } else {
        console.error('Error while requesting', file, this);
      }
    };
    xhr.send();
  }
</script>

ArrayBuffer -> Buffer ->字符集(Base64)

将ArrayBuffer改为Buffer,然后改为String。

Buffer.from(arrBuffer).toString("base64");

Just

const buffer = thisReturnsBuffers();

const blob = new Blob([buffer], {type: 'text/plain; charset=utf-8'});

blob.text().then(text => console.log(text));

Or

const stringVal = "string here";

const blob = new Blob([stringVal], {type: 'text/plain; charset=utf-8'});

blob.arrayBuffer().then(buffer => console.log(buffer));

你们为什么要把事情搞得这么复杂?