Throttle function won't run without interval constant

class Neuron {
fire() {
  console.log("Firing!");
}
Function.prototype.myThrottle = function(interval) {
// declare a variable outside of the returned function
let tooSoon = false;
return (...args) => {
  // the function only gets invoked if tooSoon is false
  // it sets tooSoon to true, and uses setTimeout to set it back to
  // false after interval ms
  // any invocation within this interval will skip the if 
  // statement and do nothing
  if (!tooSoon) {
    tooSoon = true;
    setTimeout(() => tooSoon = false, interval);
    this(...args); // confused what this piece of code does. 
  }
}


function printFire(){ return neuron.fire()}
const neuron = new Neuron();
neuron.fire = neuron.fire.myThrottle(500);
const interval = setInterval(printFire, 10);

This piece of code will output "Firing!, once every 500ms". My confusion is when I comment "const interval = setInterval(printFire, 10) ", The code does not run at all. I feel const interval should not get called if we already have neuron.fire = ...myThrottle(500). I'm just confused on the sequence of events in this piece of code. Also the line "this(...args)" is calling a function but not sure what exactly.

Very knew javascript is so all responses will be greatly appreciated. thank you!

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