What is alternative way concat in js

Question

I'm having a problem with my function flatten

Here's the code:

    function flatten(arrays) {
    return [].concat.apply([], arrays);
}

There's an error of max exceed so i tried to change the function to this:

    function flatten(arrays){
    return arrays.reduce(function(prev, curr){
        return prev.concat(curr);
    }, []);
}

the error was gone but its too slow. Is there alternative code for concat.

Answer 1

Try this ES6 spread syntax:

const array1 = [1,2,3]
const array2 = [4,5,6]
const array3 = [...array1, ...array2]
console.log(array3)