Copyright Derek O'Reilly, Dundalk Institute of Technology (DkIT), Dundalk, Co. Louth, Ireland.

Arrow Functions

Arrow functions are another way to declare functions.

// using function keyword
function name() 
{
    return "Mary"
}


// using arrow function
name = () => 
{
    return "Mary"
}

If the function has only one statement, and the function returns a value, we can remove the curly brackets and the return keyword, as shown below:

const name = () => "Mary"

Note that, if we include curly brackets (i.e. the function is in a block), then we must also include the return keyword, as shown below:

const name = () => {return "Mary"}

If a function has only one parameter, we can remove the round brackets

/* With round brackets */
const square = (number) => number * number

/* Without round brackets */
const square = number => number * number

An arrow function cannot contain a line break between its parameters (i.e. the round brackets) and its arrow.

/* Syntax error */
const result = ()
    => 1


/* This is allowed */
const result = () =>
    1

Copyright Derek O' Reilly, Dundalk Institute of Technology (DkIT), Dundalk, Co. Louth, Ireland.