Comparing the contents of two JS arrays

Question

Trying to compare to arrays in JavaScript with the following approach.

 return stack1.forEach((v, i) => v === stack2[i]);

I want to get it working but it is returning undefined instead of true or false if the arrays are the same.

Here is the full code:

const backspace_compare = function(str1, str2) {
  let stack1 = [];
  let stack2 = [];
  for (let i = 0; i < str1.length; i++) {
    str1[i] === "#" ? stack1.pop() : stack1.push(str1[i]);
  }
  for (let i = 0; i < str1.length; i++) {
    str2[i] === "#" ? stack2.pop() : stack2.push(str2[i]);
  }
  return stack1.forEach((v, i) => v === stack2[i]);
};

Any help to fix the way I'm comparing the arrays using a similar approach would be really appreciated.

`forEach` returns `undefined`, maybe you want to use `.every()` instead? — Nick Parsons, Oct 27 '19 at 11:59

score 2 · Accepted Answer · answered Dec 22 '20 at 09:31

Here are some methods I use to compare two array in JS. The method I prefer usually is JSON.stringify.

However, I feel that your method is the fastest one, just you've to use .every() in place of forEach().

let stack1 = [1, 2, 3, 4];
let stack2 = [1, 2, 3, 4];

console.log('every compare:', stack1.every((v, i) => v === stack2[i]));
// or
console.log('toString compare:', stack1.toString() === stack2.toString());
// or
console.log('JSON compare:', JSON.stringify(stack1) === JSON.stringify(stack2));
// or
console.log('short compare:', stack1+'' === stack2+'');

PS: If anyone wants to gift me a hat, then just vote up my answer, which is quite useful :) — vrintle, Dec 22 '20 at 09:34

Comparing the contents of two JS arrays

1 Answers1