Is it possible to use Array.push to add multiple values from a list? For example, currently what I'm having to do is:
Array.prototype.extend = function(arr) {
for (let elem of arr) {
this.push(elem);
}
}
let x = [1,2,3];
let y = [4,5,6];
let z = [7,8,9];
x.push(y);
x.extend(z)
console.log(x);Or, is there some way to pass the array as a single argument to the push method, or perhaps there's another Array method entirely that does this instead?
It's usually bad practice to Extend Native Types with Custom Methods. So instead of adding custom ones to the Array prototype you could:
...const x = [1,2,3];
const y = [4,5,6];
const z = [7,8,9];
x.push(y);
x.push(...z)
console.log(x);let x = [1,2,3];
const y = [4,5,6];
const z = [7,8,9];
x.push(y);
x = x.concat(z);
console.log(x);The difference being - .concat() does not directly modify the original Array, therefore the x = x.concat( assignment syntax, and the Original x array being set as a let variable.
Array.prototype.concat() isn't mutational, so you have to manually re-assign the value to the array.
x = x.concat - Added the respective let and const to make it more obvious.you can spread the array element like this
const x = [1,2,3];
const y = [4,5,6];
const z = [7,8,9];
x.push(...y);
x.push(...z)
console.log(x);
You can push multiple arguments to Array.prototype.push and they'll all be pushed to our result array, so we can "convert" our array into multiple arguments using the ES6 spread syntax.
let x = [1,2,3];
let y = [4,5,6];
x.push(...y);
console.log(x);
return or while keywords, it's not an operator. An operator is a symbol like + or * or [ ] etc that figures into the expression grammar of a language. It's kind-of splitting hairs, but it really isn't an "operator".
x.push.apply(x, y);x.pushreturns a[object Function].Function.prototype.applyreceivesthisand an argument list..apply()method on the Function prototype takes two arguments: the value to be used forthis, and an array. The array is treated as the function argument list. In modern JavaScript, it's the same asx.push(... y), which I'd use if I didn't have to worry about Internet Explorer.x.push(...y)?