html代码：
<input type="file" />
jq代码：
$('#file1').change(function(e){
var imgBox = e.target;
uploadImg($('.file1'), imgBox)
});
function uploadImg(element, tag ) {
var file = tag.files[0];
var imgSrc;
if (!/image\/\w+/.test(file.type)) {
alert("请上传图片！");
return false;
}
var reader = new FileReader();
reader.readAsDataURL(file);
reader.onload = function() {
//console.log(this.result);
imgSrc = this.result;
$(element).attr("src", imgSrc);
};
}