File upload

Hi,

 I want to set minimum size of file to be 20kb in my form. Since the upload document property has maximum size limit any way around to achieve this. I tried custom javascript but no luck? Can anyone help...

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<script>

$('document.getElementById("upload_photo")').change( function()

{

const size =

(this.files[0].size / 1024 / 1024).toFixed(2);

if (size > 4 || size < 2) {

alert("File must be between the size of 2-4 MB");

} else {

}

});

</script>

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<script>
    Filevalidation = () => {
        const fi = document.getElementById('file');
        // Check if any file is selected.
        if (fi.files.length > 0) {
            for (const i = 0; i <= fi.files.length - 1; i++) {
  
                const fsize = fi.files.item(i).size;
                const file = Math.round((fsize / 1024));
                // The size of the file.
                if (file >= 4096) {
                    alert(
                      "File too Big, please select a file less than 4mb");
                } else if (file < 2048) {
                    alert(
                      "File too small, please select a file greater than 2mb");
                } else {
                    document.getElementById('size').innerHTML = '<b>'
                    + file + '</b> KB';
                }
            }
        }
    }
</script>

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These are few codes which i tried but not working. What is syntax to get value from upload element i.e document.getElementById('file') is this right?