验证图像上传的大小，高度和宽度

Question

function displayPreview(files) {

    var reader = new FileReader();
    var img = new Image();
    reader.onload = function (e) {
        img.src = e.target.result;
        fileSize = Math.round(files.size / 1024);
        if(fileSize>50) {
            ret1=false;
            alert("File size is " + fileSize + " kb");
            return ret1;
        } else  {
            var ret1 = true;
            return ret1;
        }
    img.onload = function () {
        if(this.width!="181" && this.height!="181") {
            ret1=false;
            alert("width=" + this.width + " height=" + this.height);
            return ret1;
        } else  {
        var ret1 = true;
        return ret1;
        }
        console.log("width=" + this.width + " height=" + this.height+"File size is " + fileSize + " kb");
    };
};
    reader.readAsDataURL(files);
}   
function chkform() {
    var ret = false;
        if (document.getElementById("file").value === "") {
            console.log("empty");
        } else  {
            var file = document.getElementById("file").files[0];
            var tt=displayPreview(file);
            console.log(tt+"nis");
        }
        return ret;
}

When a user clicks on the submit button, the form has an onsubmit="return chkform();" , then my checkform checks if the id name file is empty or not.

If not, then it call the function displayPreview() . In that function I am checking whether the size is not more than 50 and width and height is not equal to width="181px" and height="181px" .

I am returning ret through which I can get the information it's returning true or false but In my checkform I am getting UNDEFINED ... why?

Edit

Added reproduction code at JSFIddle: http://jsfiddle.net/nishit_bhardwaj/zaukV/

Answer 1

Sorry I didn't work with your code but this is how you can get the filesize. After that it's easy to validate. You also could disable or hide the submit/upload-button if the filesize is incorrect:

http://jsfiddle.net/rq8nA/

JS:

$("input:file").change(function () {
       if ($(this).val() !== "") {
        var file = $('#file_select')[0].files[0];
        console.log(file.size);
       }
});

HTML:

<input type="file" name="file" id="file_select" />

I added something to get width and preview image too: http://jsfiddle.net/rq8nA/1/