var progress = new FileProgress(file, this.customSettings.upload_target);该怎么处理

var progress = new FileProgress(file, this.customSettings.upload_target);


问题1.
this.fileProgressID = "divFileProgress";   中的this指的是什么？           

问题2：
这是一个函数。 下边好像是设置什么属性，不理解这种表达方式
FileProgress.prototype.setProgress = function (percentage) {
this.fileProgressElement.className = "progressContainer green";
this.fileProgressElement.childNodes[3].className = "progressBarInProgress";
this.fileProgressElement.childNodes[3].style.width = percentage + "%";
};

问题3：
var progress = new FileProgress(file,  this.customSettings.upload_target);
这是一个函数，直接调用就行，为什么还要 new

不好意思问这么多，谢谢！



这是swfupload里边handle.js的东西

/* ******************************************

 *	FileProgress Object

 *	Control object for displaying file info

 * ****************************************** */



function FileProgress(file, targetID) {

	this.fileProgressID = "divFileProgress";



	this.fileProgressWrapper = document.getElementById(this.fileProgressID);

	if (!this.fileProgressWrapper) {

		this.fileProgressWrapper = document.createElement("div");

		this.fileProgressWrapper.className = "progressWrapper";

		this.fileProgressWrapper.id = this.fileProgressID;



		this.fileProgressElement = document.createElement("div");

		this.fileProgressElement.className = "progressContainer";



		var progressCancel = document.createElement("a");

		progressCancel.className = "progressCancel";

		progressCancel.href = "#";

		progressCancel.style.visibility = "hidden";

		progressCancel.appendChild(document.createTextNode(" "));



		var progressText = document.createElement("div");

		progressText.className = "progressName";

		progressText.appendChild(document.createTextNode(file.name));



		var progressBar = document.createElement("div");

		progressBar.className = "progressBarInProgress";



		var progressStatus = document.createElement("div");

		progressStatus.className = "progressBarStatus";

		progressStatus.innerHTML = " ";



		this.fileProgressElement.appendChild(progressCancel);

		this.fileProgressElement.appendChild(progressText);

		this.fileProgressElement.appendChild(progressStatus);

		this.fileProgressElement.appendChild(progressBar);



		this.fileProgressWrapper.appendChild(this.fileProgressElement);



		document.getElementById(targetID).appendChild(this.fileProgressWrapper);

		fadeIn(this.fileProgressWrapper, 0);



	} else {

		this.fileProgressElement = this.fileProgressWrapper.firstChild;

		this.fileProgressElement.childNodes[1].firstChild.nodeValue = file.name;

	}



	this.height = this.fileProgressWrapper.offsetHeight;



}

FileProgress.prototype.setProgress = function (percentage) {

	this.fileProgressElement.className = "progressContainer green";

	this.fileProgressElement.childNodes[3].className = "progressBarInProgress";

	this.fileProgressElement.childNodes[3].style.width = percentage + "%";

};

FileProgress.prototype.setComplete = function () {

	this.fileProgressElement.className = "progressContainer blue";

	this.fileProgressElement.childNodes[3].className = "progressBarComplete";

	this.fileProgressElement.childNodes[3].style.width = "";



};

FileProgress.prototype.setError = function () {

	this.fileProgressElement.className = "progressContainer red";

	this.fileProgressElement.childNodes[3].className = "progressBarError";

	this.fileProgressElement.childNodes[3].style.width = "";



};

FileProgress.prototype.setCancelled = function () {

	this.fileProgressElement.className = "progressContainer";

	this.fileProgressElement.childNodes[3].className = "progressBarError";

	this.fileProgressElement.childNodes[3].style.width = "";



};

FileProgress.prototype.setStatus = function (status) {

	this.fileProgressElement.childNodes[2].innerHTML = status;

};



FileProgress.prototype.toggleCancel = function (show, swfuploadInstance) {

	this.fileProgressElement.childNodes[0].style.visibility = show ? "visible" : "hidden";

	if (swfuploadInstance) {

		var fileID = this.fileProgressID;

		this.fileProgressElement.childNodes[0].onclick = function () {

			swfuploadInstance.cancelUpload(fileID);

			return false;

		};

	}

};

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