Check if Array has all Elements of Another Array - JavaScript

Check if Array has all Elements of Another Array #

To check if an array contains all of the elements of another array:

1. Call the Array.every() method on the first array.
2. Check if each element in the array is contained in the second array.
3. If the condition is met for all elements, the array has all elements of the other array.

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const arr1 = ['pizza', 'cola'];
const arr2 = ['pizza', 'cake', 'cola'];

const containsAll = arr1.every(element => {
  return arr2.includes(element);
});

console.log(containsAll); // 👉️ true

The function we passed to the Array.every method is invoked with each element of the array and should return a truthy or a falsy value.

If all invocations of the callback function return a truthy value, then the Array.every method returns true, otherwise false is returned.

If the callback function we passed to the Array.every() method returns a falsy value, then Array.every() also returns false.

Alternatively, you can use the Array.indexOf() method.

Check if Array has all Elements of Another Array using Array.every() #

To check if an array contains all of the elements of another array:

1. Call the Array.every() method on the first array.
2. Check if the index of each element is found in the second array.
3. If the condition is met for all elements, the array has all elements of the other array.

Copied!
const arr1 = ['pizza', 'cola'];
const arr2 = ['pizza', 'cake', 'cola']

const containsAll = arr1.every(element => {
  return arr2.indexOf(element) !== -1;
});

console.log(containsAll); // 👉️ true

We used the Array.every() method to iterate over the first array.

On each iteration, we check if the current element is contained in the second array.

The Array.indexOf method returns the index of the provided value in the array. If the value is not found in the array, the method returns -1.

The arr2 array contains all of the elements of arr1, therefore the return value of the Array.indexOf method will never be equal to -1.

After the Array.every() method finishes iterating, it returns true.