HTML 5のFileWriter継承拡張、メソッドまたはオブジェクトの追加

      JavaScript                               ，                      ，        FileWriter     。

function FileWriter(writer)
{
    this.writer = writer;
    // EventTarget
    this.addEventListener = function(type, listener, useCapture) {
        this.writer.addEventListener(type, listener, useCapture);
    };
    this.removeEventListener =  function(type, listener, useCapture) {
        this.writer.removeEventListener(type, listener, useCapture);
    };
    this.dispatchEvent = function(evt) {
        this.writer.dispatchEvent(evt);
    };


    // FileSaver
    const INIT = this.writer.INIT;
    const WRITING = this.writer.WRITING;
    const DONE = this.writer.DONE;
    this.__defineGetter__("readyState", function(){return this.writer.readyState;});
    this.__defineGetter__("error", function(){return this.writer.error;});
    this.__defineGetter__("fileName", function() {return this.writer.fileName;});
    this.abort = function() {
        this.writer.abort();
    };


    this.__defineGetter__("onwritestart", function(){return this.writer.onwritestart;});
    this.__defineGetter__("onprogress", function(){return this.writer.onprogress;});
    this.__defineGetter__("onabort", function(){return this.writer.onabort;});
    this.__defineGetter__("onwrite", function(){return this.writer.onwrite;});
    this.__defineGetter__("onerror", function(){return this.writer.onerror;});
    this.__defineGetter__("onwriteend", function(){return this.writer.onwriteend;});
    this.__defineSetter__("onwritestart", function(val){this.writer.onwritestart=val;});
    this.__defineSetter__("onprogress", function(val){this.writer.onprogress=val;});
    this.__defineSetter__("onabort", function(val){this.writer.onabort=val;});
    this.__defineSetter__("onwrite", function(val){this.writer.onwrite=val;});
    this.__defineSetter__("onerror", function(val){this.writer.onerror=val;});
    this.__defineSetter__("onwriteend", function(val){this.writer.onwriteend=val;});


    // FileWriter
    this.__defineGetter__("position", function(){return this.writer.position;});
    this.__defineGetter__("length", function(){return this.writer.length;});
    this.write = function(data) {
        this.writer.write(new Blob([data], {type : "text/plain;charset=UTF-8"}));
    };
    this.seek = function(offset) {
        this.writer.seek(offset);
    };
    this.truncate = function(size) {
        this.writer.truncate(size);
    };
}