JavaScript: Array.prototype.fill

New in JS2015.

arrayX.fill(value)

Replace all elements by value. Return the modified arrayX.

const xx = [0, 1, 2];
console.log(xx.fill(7)); // [ 7, 7, 7 ]
console.log(xx); // [ 7, 7, 7 ]

use with Array Constructor

const xx = Array(4).fill(0);
console.log(xx);
// [ 0, 0, 0, 0 ]

arrayX.fill(value, start_index)

Replace start from start_index

console.log([0, 1, 2, 3].fill(9, 0)); // [ 9, 9, 9, 9 ]
console.log([0, 1, 2, 3].fill(9, 1)); // [ 0, 9, 9, 9 ]
console.log([0, 1, 2, 3].fill(9, 2)); // [ 0, 1, 9, 9 ]
console.log([0, 1, 2, 3].fill(9, 3)); // [ 0, 1, 2, 9 ]
console.log([0, 1, 2, 3].fill(9, 4)); // [ 0, 1, 2, 3 ]

arrayX.fill(value, start_index, end_index)

Replace up to end_index, not including it.

console.log([0, 1, 2, 3].fill(9, 0, 0)); // [ 0, 1, 2, 3 ]
console.log([0, 1, 2, 3].fill(9, 0, 1)); // [ 9, 1, 2, 3 ]
console.log([0, 1, 2, 3].fill(9, 0, 2)); // [ 9, 9, 2, 3 ]
console.log([0, 1, 2, 3].fill(9, 0, 3)); // [ 9, 9, 9, 3 ]
console.log([0, 1, 2, 3].fill(9, 0, 4)); // [ 9, 9, 9, 9 ]