The values of the array "b" has to be removed from the array "a"

Question

I wrote the function to accomplish what was asked, but was wondering if there was a better and nicer way to do that?

function arrayDiff(a, b) {
  let myArr = [];
  for (let i = 0; i < a.length; i++) {
    if (a[i] == b[0] || a[i] == b[1]) {
      continue;
    } else {
      myArr.push(a[i]);
    }
  }
  return myArr;
}
arrayDiff([1,2,3], [2,3]) //returns [1]

What if the length of the array "b" was more than just two elements, for example 5, how could I write a better code?

@Nick, Oh, sorry. I scrolled and later found that it does have the info that. I was looking for. Thank you — coder online, Jul 24 '20 at 09:16
No worries. You can accept the proposed duplicate if you agree with it. — Nick, Jul 24 '20 at 09:17

score 1 · Answer 1 · answered Jul 24 '20 at 09:10

1

const a = [1,2,3], b = [2,3]
let result = a.filter(n=>!b.includes(n))
console.log(result)

answered Jul 24 '20 at 09:10

holydragon

6,158
6
39
62

score 1 · Accepted Answer · answered Jul 24 '20 at 09:14

You could take a single comparison by using Array#includes.

function arrayDiff(a, b) {
    let myArr = [];

    for (let i = 0; i < a.length; i++) {
        if (b.includes(a[i])) continue;
        myArr.push(a[i]);
    }

    return myArr;
}

console.log(arrayDiff([1, 2, 3], [2, 3])); // [1]

Another faster approach takes an object with O(1) fo looking for the value of b, for example with a Set.

function arrayDiff(a, b) {
    let myArr = [],
        excluding = new Set(b);

    for (let i = 0; i < a.length; i++) {
        if (excluding.has(a[i])) continue;
        myArr.push(a[i]);
    }

    return myArr;
}

console.log(arrayDiff([1, 2, 3], [2, 3])); // [1]

score 1 · Answer 3 · answered Jul 24 '20 at 09:17

You can loop the second array and get the index of the item from the first array. Then use splice to remove the item from first array

function arrayDiff(a, b) {
  let z = a;
  b.forEach((item) => {
    const getIndx = z.indexOf(item);
    if (getIndx !== -1) {
      z.splice(getIndx, 1)
    }
  });
  return z;
}
console.log(arrayDiff([1, 2, 3], [2, 3]))

The values of the array "b" has to be removed from the array "a"

3 Answers3