fileReader 上传图片

 1 function getImgSrc(target, callback) {
 2     if (window.FileReader) {
 3         var oPreviewImg = null, oFReader = new window.FileReader();
 4         oFReader.onload = function (oFREvent) {
 5             oPreviewImg = new Image();
 6             var type = target.files[0].type.split("/")[1];
 7             var src = oFREvent.target.result;
 8             oPreviewImg.src = src;
 9
10             if (typeof callback == "function") {
11                 callback(oPreviewImg, target, type, src);
12             }
13
14             return oPreviewImg.src;
15         };
16
17         return (function () {
18             var aFiles = target.files;
19             if (aFiles.length === 0) {
20                 return;
21             }
22             if (!IsImgType(aFiles[0].type)) {
23                 alert("You must select a valid image file!");
24                 return;
25             }
26
27             if (aFiles[0].size > 1024 * 1024) {
28                 target.value = "";
29                 alert(‘Please upload image file size less than 1M.‘);
30                 return;
31             }
32
33             oFReader.readAsDataURL(aFiles[0]);
34         })();
35     }
36     if (navigator.appName === "Microsoft Internet Explorer") {
37         return (function () {
38             document.getElementById("imagePreview").filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = target.value;
39         })();
40     }
41 }