Why does an array sometimes have an undefined value?

Question

JavaScript

Guys, please explain where is the miscalculation in my algorithm?

var deck = {
        allCards: ["ch-6", "ch-7", "ch-8", "ch-9", "ch-10", "ch-v", "ch-d", "ch-k", "ch-t", "bu-6", "bu-7", "bu-8"],
        randomCards: [],
        randomizer: function(min, max) {
            var i = 0;
            while(i < deck.allCards.length) {
            var rand = Math.round(Math.random() * (max-min - 1));
            var copyCard = deck.randomCards.push(deck.allCards[rand]);
            var cutCard = deck.allCards.splice(rand, 1);
            i++;
            //console.log(deck.randomCards);
            //console.log(deck.allCards);
            console.log(rand);
            console.log(cutCard);
            console.log(copyCard);
            }
        }
    };

    deck.randomizer(0, deck.allCards.length);

Answer 1

1. Let's start with the fact that while is a bad sign. desk in inner function is bad too, better use this
Refactor -

var deck = {
        allCards: ["ch-6", "ch-7", "ch-8", "ch-9", "ch-10", "ch-v", "ch-d", "ch-k", "ch-t", "bu-6", "bu-7", "bu-8"],
        randomCards: [],
        randomizer: function(min, max) {
          for(var i = 0; i < this.allCards.length; i++) {
            var rand = Math.round(Math.random() * (max - min - 1));
            this.randomCards.push(this.allCards[rand]);
            this.allCards.splice(rand, 1);
        }
    }
};
deck.randomizer(0, deck.allCards.length);

2. Then a minor mistake in the radom - forgot to add min

var deck = {
        allCards: ["ch-6", "ch-7", "ch-8", "ch-9", "ch-10", "ch-v", "ch-d", "ch-k", "ch-t", "bu-6", "bu-7", "bu-8"],
        randomCards: [],
        randomizer: function(min, max) {
          for(var i = 0; i < this.allCards.length; i++) {
            var rand = min + Math.round(Math.random() * (max - min - 1));
            this.randomCards.push(this.allCards[rand]);
            this.allCards.splice(rand, 1);
        }
    }
};
deck.randomizer(0, deck.allCards.length);

3. And, finally, a logic error - we are splicing an array, which means that its length also decreases ... but the randomness remains the same - from 0 to the previous length. You will have to remove min and max - it is impossible to add them with such logic - they will cause problems.

var deck = {
        allCards: ["ch-6", "ch-7", "ch-8", "ch-9", "ch-10", "ch-v", "ch-d", "ch-k", "ch-t", "bu-6", "bu-7", "bu-8"],
        randomCards: [],
        randomizer: function(min, max) {
          for(var i = 0; i < this.allCards.length; i++) {
            var rand = Math.round(Math.random() * (this.allCards.length - 1));
            this.randomCards.push(this.allCards[rand]);
            this.allCards.splice(rand, 1);
        }
    }
};
deck.randomizer();

4. And finally, the correct logic:

var deck = {
        allCards: ["ch-6", "ch-7", "ch-8", "ch-9", "ch-10", "ch-v", "ch-d", "ch-k", "ch-t", "bu-6", "bu-7", "bu-8"],
        randomCards: [],
        randomizer: function(min, max) {
          for(var i = 0; i < this.allCards.length; i++) {
            var rand = min + Math.round(Math.random() * ((max > this.allCards.length ? this.allCards.length : max) - min - 1));
            this.randomCards.push(this.allCards[rand]);
            this.allCards.splice(rand, 1);
        }
    }
};
deck.randomizer(0, deck.allCards.length);

Answer 2

flip a coin