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filter

The filter() method returns a shallow copy of a portion of a given array that has been filtered down to only the elements of the given array that pass the test implemented by the provided function.

Syntax​

// Using Arrow function
filter((element) => { /* … */ } )
filter((element, index) => { /* … */ } )
filter((element, index, array) => { /* … */ } )

// Using Callback function
filter(callbackFn)
filter(callbackFn, thisArg)

// Using Inline callback function
filter(function(element) { /* … */ })
filter(function(element, index) { /* … */ })
filter(function(element, index, array){ /* … */ })
filter(function(element, index, array) { /* … */ }, thisArg)

Parameters​

The callback function is a predicate, it return the elements only when test condition satisfies true.

The callBack function have following arguments

  • element: The current element being processed.

  • index: The index of the current element being processed.

  • array: The array at which map is called upon.

  • thisArg: The value to be used as this when calling the callback function.

Examples​

Using with array​

let array = [2,15,12,48,46,23,55];
var result = array.filter((item) => (item % 2 !== 0));
console.log(result);

This example is to find the odd number from the array. By checking the condition item % 2 !== 0, if the condition is true current element is returned to the variable result. If not it is not returned.

Using with object​

var people = [{
    id: 1,
    name: "David",
    age: 28
}, {
    id: 2,
    name: "Sara",
    age: 35
}, {
    id: 3,
    name: "Jane",
    age: 21
}, {
    id: 3,
    name: "Peter",
    age: 55
}];
let young = people.filter(person => person.age < 35);
console.log(young);

The filter() method accepts a test function, and returns a new array young containing only the elements of the original array that pass the test condition person.age < 35.