在js中使用XMLHTTPREQUEST发送base64图像数据“ POST”

Question

I am trying post base64 data to server but i got one error "Microsoft JScript runtime error: Unable to get value of the property 'addEventListener': object is null or undefined" below i had attached the error screen shot any help thanks.

            var imagefile = canvas.toDataURL("image/png");
            imagefile = imagefile.replace("data:image/png;base64,", "");
            var oXHR = new XMLHttpRequest();
            oXHR.upload.addEventListener('loadstart', uploadFinish, false);
            oXHR.upload.addEventListener('progress', uploadProgress, false);
            oXHR.upload.addEventListener('error', uploaderror, false);
            oXHR.open('POST',"http://demo.donelook.com/eyewearweb/levellens.aspx",true);
            oXHR.send(imagefile);

Answer 1

我想你要：

oXHR.addEventListener('loadstart', uploadFinish, false);

Answer 2

There is a mistake in oXHR.upload.addEventListener , should be oXHR.addEventListener . Another problem is addEventListener is not supported by all browsers. You have to do something like this if you're using pure javascript.

if (!oXHR.addEventListener) {
    oXHR.attachEvent("loadstart", uploadFinish);
}
else {
    oXHR.addEventListener("loadstart", uploadFinish, false);
}

You could write this as a separate function and reuse it to ensure browser compatibility. Like this:

function addEventListener(element,type, listener, useCapture){
     if (!element.addEventListener) {
        element.attachEvent(type, listener);
     }
     else {
        element.addEventListener(type, listener, useCapture);
     }
}

Your code:

var imagefile = canvas.toDataURL("image/png");
 imagefile = imagefile.replace("data:image/png;base64,", "");
 var oXHR = new XMLHttpRequest();
 addEventListener(oXHR,'loadstart', uploadFinish, false);
 addEventListener(oXHR,'progress', uploadProgress, false);
 addEventListener(oXHR,'error', uploaderror, false);
 oXHR.open('POST',"http://demo.donelook.com/eyewearweb/levellens.aspx",true);
 oXHR.send(imagefile);