$(function () {
  // document.getElementById('submit').addEventListener('click', debounce(submitFn));
  document.getElementById('submit').addEventListener('click', submitFn.debounce(1));
})

function submitFn (val) {
  console.log( $('#inputVal').val() );
  console.log(this);
  console.log(val);
}

Function.prototype.debounce = function () {
  const Fn = this;
  let flag = null;
  const args = arguments;
  return function () {
    let firstRun = !flag;
    if (flag) { clearTimeout(flag) };
    if (firstRun) {
      Fn.apply(this, args)
    }
    flag = setTimeout(() => {
      flag = null;  
    }, 1000)
  }
}


const debounce = function (Fn) {
  let flag = null;
  return function () {
    let firstRun = !flag;
    if (flag) { clearTimeout(flag) };
    if (firstRun) {
      Fn.apply(this, arguments)
    }
    flag = setTimeout(() => {
      flag = null;
    }, 500)
  }
}