Writing Arrow Functions with Parameters

JS

function run_function() {
  "use strict";
  const double_me = (item) => item * 2;
  write_result(double_me(2));
  console.log(double_me(2));
  return double_me(2);
}

// write this function in one line example
/*
var myConcat = function(arr1, arr2) {
  "use strict";
  return arr1.concat(arr2);
};
*/

"use strict";
const myConcat = (arr1, arr2) => arr1.concat(arr2);
console.log(myConcat([1, 2], [3, 4, 5]));

// this is a common function just to write the content into the result div
function write_result(result) {
  var result_html = document.getElementById("result");
  result_html.innerHTML = result;
}

HTML

<div id='result' class='mb-3 alert alert-primary'>..</div>
<button onclick='run_function();' class='btn btn-primary mb-1'>Run Function</button>

Working Result

Test Result Below