H5的FileReader分布读取文件应该如何使用以及其方法简介

/*

* 文件读取模块

* file  文件对象

* events 事件回掉对象 包含 success , load, progress

*/

var FileLoader = function (file, events) {

    this.reader = new FileReader();

    this.file = file;

    this.loaded = 0;

    this.total = file.size;

    //每次读取1M

    this.step = 1024 * 1024;

    this.events = events || {};

    //读取第一块

    this.readBlob(0);

    this.bindEvent();

}

FileLoader.prototype = {

    bindEvent: function (events) {

        var _this = this,

            reader = this.reader;

        reader.onload = function (e) {

            _this.onLoad();

        };

        reader.onprogress = function (e) {

            _this.onProgress(e.loaded);

        };

        // start 、abort、error 回调暂时不加

    },

    // progress 事件回掉

    onProgress: function (loaded) {

        var percent,

            handler = this.events.progress;//进度条

        this.loaded += loaded;

        percent = (this.loaded / this.total) * 100;

        handler && handler(percent);

    },

    // 读取结束（每一次执行read结束时调用，并非整体）

    onLoad: function () {

        var handler = this.events.load;

        // 应该在这里发送读取的数据

        handler && handler(this.reader.result);

        // 如果未读取完毕继续读取

        if (this.loaded < this.total) {

            this.readBlob(this.loaded);

        } else {

            // 读取完毕

            this.loaded = this.total;

            // 如果有success回掉则执行

            this.events.success && this.events.success();

        }

    },

    // 读取文件内容

    readBlob: function (start) {

        var blob,

            file = this.file;

        // 如果支持 slice 方法，那么分步读取，不支持的话一次读取

        if (file.slice) {

            blob = file.slice(start, start + this.step);

        } else {

            blob = file;

        }

        this.reader.readAsText(blob);

    },

    // 中止读取

    abort: function () {

        var reader = this.reader;

        if(reader) {

            reader.abort();

        }

    }

}