filter() – filters elements that pass a test

Array.filter() function is used to filter elements in this array based on a filtering function.

Syntax

array.filter( function, thisValue )

• array is the given array.
• every is inbuilt array method name.
• function a function to run for every element. the definition of the function is function(element, index, arr). the function must return a boolean value of true or false.
  • element is the current element in the array.
  • index of the current element [optional argument].
  • arr is the array of current element [optional argument].
• thisValue is a value passed to the function as its this value [optional argument].

filter() method creates and returns a new array with the elements from the original array that return true for the given function.

Examples

1. Filter even numbers from the given numeric array nums.

function isEven(num) {
    if (num % 2 == 0) {
        return true;
    } else {
        return false;
    }
}

nums = [4, 1, 8, 0, 2, 3, 5];
evenNumbers = nums.filter(isEven);
console.log(evenNumbers);

2. Filter non-empty strings from the given string array names.

function isNonEmptyString(item) {
    if (item.length !== 0) {
        return true;
    } else {
        return false;
    }
}

names = ["apple", "banana", "", "cherry", "", "mango"];
nonEmptyNames = names.filter(isNonEmptyString);
console.log(nonEmptyNames);