change src of img tag with input file

Question

I have a input and img tag like this in my HTML code:

<input type="file" name="img2" id="chooseimg" onchange="readURL(this);">

<img id="img-edt" src="l1.png" alt="your image" width="502" height="319"/>

And in js i use this code to change image:

function readURL(input) {
 if (input.files && input.files[0]) {
     var reader = new FileReader();
     reader.onload = function(e) {
         $('#img-edt')
             .attr('src', e.target.result)
             .width(502)
             .height(319);
     };
     reader.readAsDataURL(input.files[0]);
 }
 showDimension();
 }

After that image load,i need to know the dimension of original image,so i use this function:

function showDimension() {
 var mm = document.getElementById("img-edt");
 var ww = mm.naturalWidth;
 var hh = mm.naturalHeight;
 var x = document.getElementById("teeest");
 x.innerHTML = "w is: " + String(ww) + "h is: " + String(hh);
 }

But the problem is that always it returns size of previous image. please help me with this problem.

Answer 1

Since changing an image is an asynchronous operation, you have to move showDimension() function into onload callback as well:

function readURL(input) {
    if (input.files && input.files[0]) {
        var reader = new FileReader();
        reader.onload = function (e) {
            $('#img-edt')
                .attr('src', e.target.result)
                .width(502)
                .height(319);
            showDimension();
        };
        reader.readAsDataURL(input.files[0]);
    }
}