Remove Undefined Values from an Array in JavaScript

Remove Undefined Values from an Array #

To remove all undefined values from an array:

1. Call the filter() method, passing it a function.
2. The function should check whether each element is not equal to undefined.
3. The filter method returns a new array, containing only the elements that satisfy the condition.

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 array element.

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 only include defined values in the results array.

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. On each iteration check if the current 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 pass to the Array.forEach method gets called with each element in the array.

The results array does not contain any elements with value undefined.

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