.filter()

The .filter() array method creates a new array with all elements that pass the test from the provided function.

Syntax

// Arrow function
array.filter(element => { ... })
array.filter((element, index) => { ... })
array.filter((element, index, array) => { ... })

.filter() takes the following parameters:

• element: The current element being processed in the array.
• index (optional): The index of the current element being processed in the array.
• array (optional): The array filter was called upon.

The method will return a new array with the elements that pass the test.

Note: If no elements pass the test, an empty array will be returned.

Examples

Filtering out all small values:

const numbers = [6, 44, 87, 1, 197, 22];

const filteredNumbers = numbers.filter((num) => num >= 10);

console.log(filteredNumbers);
// Output: [44, 87, 197, 22]

Filtering by index:

const numbers = [6, 44, 87, 1, 197, 22];

const filterByIndex = numbers.filter((element, index) => {
  return index % 2 === 0;
});

console.log(filterByIndex);
// Output: [6, 87, 197]

Filtering out names that don’t begin with the given character:

const names = ['Jim', 'Bob', 'Sarah', 'Alex', 'James', 'Sam', 'Peter'];

const filteredNames = (char, array) => {
  return array.filter((name) => name[0].toLowerCase() === char);
};

console.log(filteredNames('j', names));
// Output: ["Jim", "James"]

Codebyte Example

The example below shows .filter() being used to filter an array of objects, called techCompany, using two criteria.

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