Check out example codes for "javascript upload file without input". It will help you in understanding the concepts better.

Code Example 1

<style>
 input {
    display: block;
    visibility: hidden;
    width: 0;
    height: 0;
}
</style>

<input type="file" name="somename" size="chars">
<button>Choose File</button>

<script>
$('button').click(function(){
    $('input').click();
});
</script>

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