Basic Usage

Creating

Shorthand method:

var myArray = Array('apple', 'banana', 'carrot');

Length

Iterating

You can use a standard for-loop:

var myArray = Array('apple', 'banana', 'carrot');
for (var i = 0, j = myArray.length; i < j; i++) {
	console.log(myArray[i]);
}

or you could use a higher-order function (see below).

var myArray = Array('apple', 'banana', 'carrot');
function showFruit(fruit) {
	console.log(fruit);
}
myArray.forEach(showFruit);

Do not use the for each ($item in $array) {... construct to loop over an array.

Higher-Order Array Functions

In mathematics and computer science, a higher-order function is a function that does at least one of the following:

• takes one or more functions as an input
• outputs a function

From a practical perspective, Javascript’s Array object has the following prototype functions that are higher-order (Mozilla calls these Iteration Methods).

Most common

map()

reduce()

Uses an accumulator to get a single value.

var myArray = Array(
	{age: 15, name: 'Samantha'},
	{age: 46, name: 'Craig'},
	{age: 52, name: 'Nancy'},
	{age: 8, name: 'Alison'},
	{age: 77, name: 'Betty'}
);
function sumAge(previousValue, currentValue, index, array) {
	//Because currentValue is an object, you need to return an object.
	return {
		age: previousValue.age + currentValue.age
	};
}
var ageSummation = myArray.reduce(sumAge);
console.log('Average age is ' + (ageSummation.age / myArray.length)); //39.6

forEach()

find()