js图片预览

function viewPic(id, imgId) {
    var reads = new FileReader();
    f = document.getElementById(id).files[0];
    if (f) {
        reads.readAsDataURL(f);
        reads.onload = function (e) {
            document.getElementById(imgId).src = this.result;
            $("#" + imgId).css("display", "block");
        };
    }
}