Is item in array?

Task: Check if item is in array. Return boolean.

for loop

function forHas(arr, x) {
  for (let item of arr) {
    if (item === x) {
      return true;
    }
  }
  return false;
}

Index is not -1

function compareHas(arr, x) {
  return arr.indexOf(x) !== -1;
}

Using includes

function includesHas(arr, x) {
  return arr.includes(x);
}

Some

function someHas(arr, x) {
  return arr.some(item => item === x);
}

Bitwise not indexOf

If you want to don't understand your code.

function bitwiseHas(arr, x) {
  return !!~arr.indexOf(x);
}

~-1 === 0, then !!0 === false, any other number than 0 is truthy.

With Set

function setHas(arr, x) {
  return new Set(arr).has(x);
}

* Filter 😵

function filterHas(arr, x) {
  return !!arr.filter(item => x === item).length; // 😂
}

* Reduce 🐱‍👤

function reduceHas(arr, x) {
  return arr.reduce(function (has, item) {
    if (!has) return item === x;
    return has;
  }, false); // 💣
}

What piece of code are you using for that task? What is the strangest, but efficient way to do that?

Comments

[martin2844]

An interesting add to this article would be benchmarks to see which is the most efficient method?

[Hub]

I made a quick benchmark with that code.
jsbench.me/5xkmowvikx/1

It seems that includes is the fastest on Chrome, on Firefox indexOf and bitwise is the winner. On Firefox on Android seems like its includes and bitwise are winners.

The slowest method is using Set.