Javascript functions

Functions

function say_hello() {
    console.log("hello")
    return true
}
say_hello()

See Also javascript arguments

Return Values

javascript functions cannot return more than one variable.

First Class Functions

Functions can be assigned to variables,
passed as arguments,
returned from functions.

var do_thing = function() { console.log("hello") }
do_thing()

Anonymous Functions

Functions do not need to be named.

myButton.onclick = function() {
    alert('hello')
}

Lambda Functions

Basics

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions

Also referred to as arrow function expressions.

(a, b) => a + b + 100     // lambda expression w/ args
() => console.log('hi')   // lambda expression w/o args

Currying

const sum = a => b => { a + b };
sum(1)(2);  // 3

const plus_one = sum(1);
plus_one(2); // 3

Partials

Closures

Javascript supports functions defined inside functions.

function foo() {
    function bar() {
        console.log('baz')
    }
    bar()
}

Binding this

bind() lets you change the value of this within a method.

B = { x: 2 }

class A {
  x = 1
  constructor() { this.printb = this.printx.bind(B) }  // this.printb uses value of 'x' from 'B'
  printx() { console.log(this.x); }                    // this.printx uses value of 'x' from 'A'
}

const a = new A().printx()
a.printx()
a.printb()