I have been reading online and some places say it isn't possible, some say it is and then give an example and others refute the example, etc.
How do I declare a 2 dimensional array in JavaScript? (assuming it's possible)
How would I access its members? (
myArray[0][1]ormyArray[0,1]?)
55 Answers
var items = [
[1, 2],
[3, 4],
[5, 6]
];
console.log(items[0][0]); // 1
console.log(items[0][1]); // 2
console.log(items[1][0]); // 3
console.log(items[1][1]); // 4
console.log(items);You simply make each item within the array an array.
var x = new Array(10);
for (var i = 0; i < x.length; i++) {
x[i] = new Array(3);
}
console.log(x);Similar to activa's answer, here's a function to create an n-dimensional array:
function createArray(length) {
var arr = new Array(length || 0),
i = length;
if (arguments.length > 1) {
var args = Array.prototype.slice.call(arguments, 1);
while(i--) arr[length-1 - i] = createArray.apply(this, args);
}
return arr;
}
createArray(); // [] or new Array()
createArray(2); // new Array(2)
createArray(3, 2); // [new Array(2),
// new Array(2),
// new Array(2)]
How to create an empty two dimensional array (one-line)
Array.from(Array(2), () => new Array(4))
2 and 4 being first and second dimensions respectively.
We are making use of Array.from, which can take an array-like param and an optional mapping for each of the elements.
Array.from(arrayLike[, mapFn[, thisArg]])
var arr = Array.from(Array(2), () => new Array(4));
arr[0][0] = 'foo';
console.info(arr);The same trick can be used to Create a JavaScript array containing 1...N
Alternatively (but more inefficient 12% with n = 10,000)
Array(2).fill(null).map(() => Array(4))
The performance decrease comes with the fact that we have to have the first dimension values initialized to run .map. Remember that Array will not allocate the positions until you order it to through .fill or direct value assignment.
var arr = Array(2).fill(null).map(() => Array(4));
arr[0][0] = 'foo';
console.info(arr);
