Functions

Creating a basic named function. Here I will write the function a file called function.js, and load it to our empty index.html. Later I will use console to call and print the results.

function multiply(a, b) {
    var result = a * b; 
    return result;
}

Now on the console:

mult = multiply(6, 9); 
console.log(mult); 

54 

console.log(multiply(17, 4))

68

Anonymous function

Anonymous functions do not have name, they are tied to variables or events.

var a = 5/6; 
var b = 7/9; 

var theBiggest = function() {
    a > b ? result = a : result = b;
    return result; 
}

var biggerRatio = theBiggest()  // We invoke the function by adding () to the end of the variable 
console.log(biggerRatio)

0.8333333333333334

Note that if you don't add the parenthesis () in the end of the variable, and console.log it will print the function.

We can have arguments to an anonymous function as well:

var theBiggest2 = function(x, y) {
    x > y ? result = x : result = y; 
    return result;
}

var biggerRatio2 = theBiggest2(3/4, 5/7); 
console.log(biggerRatio2)

0.75

Immediately invoked function expression

In this case the function is invoked as soon as the browser encounters them. It can populate our variable straightaway. We wrap the whole function inside a parenthesis (), followed by another set of parenthesis to pass the variables.

var theBiggest3 = (function(a, b) {
    a > b ? result = a : result = b;
    return result; 
})(3/4, 5/7)

console.log(theBiggest3);

0.75

Arrow functions

This is pretty much the same as anonymous function but with concise syntax:

var total = (price) => {
    return price + price * 7/100; 
}; 

console.log(total(100));