JS: FileReader return result

function ReadFile(file) {
    var reader = new FileReader();
    reader.onload = (function (file) {
        return function () {
            console.log(this.result);
            console.log(arguments);
            return this.result;
        };
    })(file);

    reader.readAsBinaryString(fileInput.files[0]);
};

run.onclick = function(){

    if (mod === 'single') {
        if (e) {
            console.log(
        }
    }else { 
        let result = readFile()
    }
};

<input id="file" class="ui animated button" type="file">
    <div id="run" class="ui right floated animated fade button" tabindex="0">
       <div class="hidden content">Run</div>
       <div class="visible content">
       <i class="tasks icon"></i>
     </div>
</div>