Every Time On A Button Click, Generate A UNIQUE Random Number In A Range Of 1 - 100 - JavaScript

I have a function. Every time I call the function, it should return a UNIQUE (for example, if I call this function 90 times, it should have given 90 different numbers) random numbe

Solution 1:

Make an array of a 100 numbers an cut the chosen number out each time you call it:

var unique = (function() {                             // wrap everything in an IIFE
  var arr = [];                                        // the array that contains the possible values
  for(var i = 0; i < 100; i++)                         // fill it
    arr.push(i);
  
  return function() {                                  // return the function that returns random unique numbers
    if(!arr.length)                                    // if there is no more numbers in the array
      return alert("No more!");                        // alert and return undefined
    
    var rand = Math.floor(Math.random() * arr.length); // otherwise choose a random index from the array
    return arr.splice(rand, 1) [0];                    // cut out the number at that index and return it
  };
})();

console.log(unique());
console.log(unique());
console.log(unique());
console.log(unique());