Main Array Functions in JavaScript

 

Here is a summary of some major array functions with examples in JavaScript.

Code snippet to define an example of an array

var persons = new Array(); var object = { name: "Mary", age:22, email: "mary@gmail.com"}; persons.push(object); object = { name: "Jack", age:25, email: "jack@gmail.com"}; persons.push(object); object = { name: "Bob", age:37, email: "bob@gmail.com"}; persons.push(object);

Function	Definition	Result Type	Code Snippet	Code Output
filter	Gets the elements satisfying the testing function	Array	const filtered_persons = persons.filter(p => p.age < 30); console.log(filtered_persons);	[{name: 'Mary', age: 22, email: 'mary@gmail.com'}, {name: 'Jack', age: 25, email: 'jack@gmail.com'}]
map	Gets elements that have a subset of the original elements’ properties	Array	const persons_name = persons.map(p => p.name); console.log(persons_name);	['Mary', 'Jack', 'Bob']
join	Concatenates all array elements as a string with a separator	String	const joined_name = persons.map(p => p.name).join(', '); console.log(joined_name);	Mary, Jack, Bob
find	Returns the first element satisfying the testing function	object	const first_found = persons.find(p => p.age < 30); console.log(first_found);	{name: 'Mary', age: 22, email: 'mary@gmail.com'}
findIndex		number	const first_index = persons.findIndex(p => p.age > 25); console.log(first_index);	2
reduce	Reduces array elements to a single value after applying a custom function	It depends on the single value you want to get like number, string, etc.	const initAge = 0; const sumAges = persons.reduce( (accumulator, currentPerson) => accumulator + currentPerson.age, initAge, ); const meanAge = Math.round(sumAges/persons.length); console.log(meanAge);	28