responseType属性可以设置server返回字节的解析类型.比如"arraybuffer", “blob”, “document”, “json”, and “text”,对应的返回的类型就是ArrayBuffer, Blob, Document, JSON, or string

arraybuffer

使用arraybuffer接收png图片,并使用8bit unsigned integer array处理 raw bytes.只是处理字节,并没有解码图片,解码图片需要png decoding library

var oReq = new XMLHttpRequest();oReq.open("GET", "/myfile.png", true);oReq.responseType = "arraybuffer";oReq.onload = function (oEvent) {var arrayBuffer = oReq.response; // Note: not oReq.responseTextif (arrayBuffer) {var byteArray = new Uint8Array(arrayBuffer);for (var i = 0; i < byteArray.byteLength; i++) {// do something with each byte in the array}}};oReq.send(null);

blob

使用Blob来读取binary file

var oReq = new XMLHttpRequest();oReq.open("GET", "/myfile.png", true);oReq.responseType = "blob";oReq.onload = function(oEvent) {var blob = oReq.response;// ...};oReq.send();

字符串处理二进制

function load_binary_resource(url) {var req = new XMLHttpRequest();req.open('GET', url, false);//XHR binary charset opt by Marcus Granado []req.overrideMimeType('text\/plain; charset=x-user-defined');req.send(null);if (req.status != 200) return '';return req.responseText;}var filestream = load_binary_resource(url);var abyte = filestream.charCodeAt(x) & 0xff; // throw away high-order byte (f7)

参考:

/en-US/docs/Web/API/XMLHttpRequest/Sending_and_Receiving_Binary_Data

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