text box doesn't update when I push the button

Question

I have example here: code example .

HTML code:

<input id="uploadFile" placeholder="Choose File" disabled="disabled" />
<div class="file-upload btn btn-primary">
    <span>Upload</span> 
    <br> 
    <input id="uploadBtn" class="upload" type="file">
</div>

CSS code:

.btn {
    border: 1px solid transparent;
    border-radius: 4px;
    cursor: pointer;
    display: inline-block;
    font-size: 14px;
    font-weight: normal;
    line-height: 1.42857;
    margin-bottom: 0;
    padding: 6px 12px;
    text-align: center;
    vertical-align: middle;
    white-space: nowrap;
}

.file-upload input.upload {
    cursor: pointer;
    font-size: 20px;
    margin: 0;
    opacity: 0;
    padding: 0;
    position: absolute;
    right: 0;
    top: 0;
}

.file-upload {
    margin-left: 10px;
    overflow: hidden;
    position: relative;
}
.btn-primary {
    background-color: #428bca;
    border-color: #357ebd;
    color: #fff;
}

JavaScript code:

document.getElementById("uploadBtn").onchange = function () {
    document.getElementById("uploadFile").value = this.value;
};

In JSFiddle site, when I push the upload button, the text box are updated, but when I copy the code to files, and run it under Firefox Mozilla, the text box doesn't update.

I take reference from this site: How to Style a HTML file upload button in Pure CSS

Any suggestions?

Answer 1

Your JS does not work since the uploadBtn is not created when you are trying to add the onchange listener. Try waiting for the window to load.

window.onload = function() {
   document.getElementById("uploadBtn").onchange = function () {
      document.getElementById("uploadFile").value = this.value;
   };
};