javascript - XmlHttpRequest onload `this` 属性

Question

给定下面的代码，_onChunkComplete 方法中的this 是XHR 请求。这是有道理的。有没有办法让它成为实际的 Uploader 对象？

   function Uploader(file, options) {    
        // ... code here ....
        this.upload_request = new XMLHttpRequest();
        this.upload_request.onload =  this._onChunkComplete;
    }

    Uploader.prototype = {
        // ... code here ...
        _onChunkComplete: function() {
            if (this.range_end === this.file_size) {
                console.log('done');
                return;
            }
            this.range_start = this.range_end;
            this.range_end = this.range_start + this.chunk_size;
            if (!this.is_paused) {
                this._upload();
            }
        }
        // ... mode code here...
    };

    var test = new Uploader(formFile, {});
    test.start();

Answer 1

使用bind :

this.upload_request.onload = this._onChunkComplete.bind(Uploader)

The bind() method creates a new function that, when called, has its this keyword set to the provided value, with a given sequence of arguments preceding any provided when the new function is called.