Remove Undefined Values from an Array in JavaScript

Remove Undefined Values from an Array #

To remove all undefined values from an array:

1. Use the Array.filter() method to iterate over the array.
2. Check if each value is not equal to undefined and return the result.
3. The filter() method will return a new array that doesn't contain any undefined values.

Copied!
const arr = ['a', undefined, 'b', undefined, 'c', undefined];

const results = arr.filter(element => {
  return element !== undefined;
});

console.log(results); // 👉️ ['a', 'b', 'c']

The function we passed to the Array.filter method gets invoked with each element in the array.

If the function returns a truthy value, the element gets added to the new array.

We explicitly check if each element is not equal to undefined to exclude all undefined values.

An alternative approach is to use the forEach method.

To remove all undefined values from an array:

1. Create an empty array that will store the results.
2. Use the forEach() method to iterate over the array.
3. Check if each element is not equal to undefined.
4. If the condition is met, push the element into the results array.

Copied!
const arr = ['a', undefined, 'b', undefined, 'c', undefined];

const results = [];

arr.forEach(element => {
  if (element !== undefined) {
    results.push(element);
  }
});

console.log(results); // 👉️ ['a', 'b', 'c']

The function we passed to the Array.forEach method gets called with each element in the array.

The results array does not contain any undefined values.

Further Reading #

• Find the Odd Numbers in an Array using JavaScript
• Find the Even numbers in an Array using JavaScript
• Get a random Element from an Array using JavaScript
• Get Multiple Random Elements from an Array in JavaScript
• Add Array of Values to an Existing Set in JavaScript
• Create a Map from an Array using JavaScript
• Check if a Value is NOT in an Array using JavaScript
• How to Flatten an Array using JavaScript
• Convert an Array to JSON using JavaScript
• Create an Object from Two Arrays in JavaScript
• Convert an Object to an Array of Objects in JavaScript
• Convert an Array of Objects to a Map in JavaScript