JSFiddle - React, Tailwind, and code Playground

by Alex Alex

HTML

<input type="file" multiple>

JavaScript

var filesSizes = [],
    files;
document.querySelector('input').addEventListener('change', function () {
    filesSizes = [];
    files = [].slice.call(this.files);
    files.forEach(function (file, index) {
        var duplicateIndex = filesSizes.indexOf(file.size);
        if (duplicateIndex > -1) {
            console.log(file, files[duplicateIndex]);
        } else {
            filesSizes.push(file.size);
        }
        files[file.name] = file.size;
    });
});