JS: Array.prototype.concat
arrayX.concat(new1, new2, etc)
- Return a new array by joining arguments to the array. Each argument can be any type. If it is a array, it will be flattened 1 level (That is, remove the outmost brackets).
// example of using array.concat() const xx = [1]; console.log(xx.concat(2)); // [ 1, 2 ] // add a object console.log(xx.concat({ k9: 9 })); // [ 1, { k9: 9 } ] // var unchanged console.log(xx); // [1]
// adding an array flattens it 1 level const xx = [1]; console.log(xx.concat([2, [3]])); // [ 1, 2, [ 3 ] ]
To add without flatten, use push. See: Array.prototype.push .
For how to flatten nested array, see: Array.prototype.flat .