Combine 2 objects from 2 arrays in a loop?

Question

I'm creating a deck of cards (an array of card objects) by combining an array of suit objects, and an array of card objects, using javascript.

I'm using a forEach loop to loop through the suits, and nested is a map loop for the cards.

The console.log is returning the correct object to push to the new array, however the .push() is only appending a combined object using the last suit and the last card.

Where am I going wrong with this?

I have tried multiple different loops and methods to append to a new array without luck. Console.log() returns the correct value, but I am unable to push the correct combined objects to a new array.

  // Deck of Cards var suits = [ { suit: "clubs", color: "black" }, { suit: "spades", color: "black" }, { suit: "hearts", color: "red" }, { suit: "diamonds", color: "red" } ]; var family = [ { name: "2", value: 2 }, { name: "3", value: 3 }, { name: "4", value: 4 }, { name: "5", value: 5 }, { name: "6", value: 6 }, { name: "7", value: 7 }, { name: "8", value: 8 }, { name: "9", value: 9 }, { name: "10", value: 10 }, { name: "J", value: 10 }, { name: "Q", value: 10 }, { name: "K", value: 10 }, { name: "A", value: 1 }, ]; var deck = new Array(); suits.forEach(function (x) { var arr = family.map((y) => { var obj = Object.assign(x, y); console.log(obj); deck.push(obj); return obj; }); console.log(arr); }); console.log(deck); 

Answer 1

try Object.assign({}, x, y) instead of Object.assign(x, y) . Currently you're manipulating the object that is x, by adding all properties of y to it.

 // Deck of Cards var suits = [ {suit: "clubs",color: "black"}, {suit: "spades",color: "black"}, {suit: "hearts",color: "red"}, {suit: "diamonds",color: "red"} ]; var family = [ {name: "2",value: 2}, {name: "3",value: 3}, {name: "4",value: 4}, {name: "5",value: 5}, {name: "6",value: 6}, {name: "7",value: 7}, {name: "8",value: 8}, {name: "9",value: 9}, {name: "10",value: 10}, {name: "J",value: 10}, {name: "Q",value: 10}, {name: "K",value: 10}, {name: "A",value: 1}, ]; var deck = new Array(); suits.forEach(function(x){ var arr = family.map( (y) => { var obj = Object.assign({}, x, y); deck.push(obj); return obj; }); }); console.log(deck); 

Answer 2

Object.assign(x,y) will put the values of y onto x . You want to leave x alone, so store your properties in a new Object using Object.assign({}, x,y) . Consider the demo below:

 var suits = [ {suit: "clubs",color: "black"}, {suit: "spades",color: "black"}, {suit: "hearts",color: "red"}, {suit: "diamonds",color: "red"} ]; var family = [ {name: "2",value: 2}, {name: "3",value: 3}, {name: "4",value: 4}, {name: "5",value: 5}, {name: "6",value: 6}, {name: "7",value: 7}, {name: "8",value: 8}, {name: "9",value: 9}, {name: "10",value: 10}, {name: "J",value: 10}, {name: "Q",value: 10}, {name: "K",value: 10}, {name: "A",value: 1}, ]; const tmp = suits.reduce((acc, s) => { return acc.concat(family.map(f => { return Object.assign({}, f, s); })); }, []); const pre = document.createElement("pre"); pre.innerHTML = JSON.stringify(tmp, null, 4); document.body.appendChild(pre); 

Answer 3

If you can use flatmap , then it can be made significantly simpler:

 const suits = [{ suit: "clubs", color: "black" }, { suit: "spades", color: "black" }, { suit: "hearts", color: "red" }, { suit: "diamonds", color: "red" }] const family = [{ name: "2", value: 2 }, { name: "3", value: 3 }, { name: "4", value: 4 }, { name: "5", value: 5 }, { name: "6", value: 6 }, { name: "7", value: 7 }, { name: "8", value: 8 }, { name: "9", value: 9 }, { name: "10", value: 10 }, { name: "J", value: 10 }, { name: "Q", value: 10 }, { name: "K", value: 10 }, { name: "A", value: 1 }] const deck = suits.flatMap(s => family.map(f => ({...s, ...f}))) console.log(deck) 

A side note, there seems to be a strong convention (presumably from Bridge) of ordering the suits clubs/diamonds/hearts/spades. In English that's easy to remember since they're alphabetic.)