JavaScript Array Deep Dive : Iterating Through Array

Since an array is a collection of elements of objects, values, etc.  The most common function performed on it is to iterate through each elements of the array.  The most frequent way to do that is with a for loop.

Let's say you have an array with the following:

var numbers = ["one","two","three","four","five"];

The numbers array above contains five string elements, which also has a indexes associated with the it.  There's also a length that is defined with each array that we will use for the for loop we are about to write.  So what do the you length of the numbers array will be?

If we output the array to the browser with the statement console.log(numbers.length) do you think we will get the length to be 5 or 4?

If you guess 5 you are correct because there are five elements in the array.  However, the arrays have zero based indexes therefore the index is always length -1

for(var i = 0; i < numbers.length; i++)
{
     console.log(numbers[i]);
}

JavaScript Array Deep Dive: Adding and Deleting Elements Array.push(), Array.unshift(), and delete

When you define an object as an Array in JavaScript you get the benefits of inheriting some useful methods with it.  Some of the common methods are those that allows you to add and delete elements from an array.  The .push() method adds an element at the end of the array, the unshift() method adds an element at the beginning of the array.  The delete keyword deletes an element at the specified index.

Let say you have an the following array:

var numbers = [3,4];

If you output the array in the browser console you will see that the array has two elements with the number 3 occupying index 0 and the number 4 occupying index 1.

JavaScript Array Deep Dive: Reading and Assigning Values To Array

In the previous post we created arrays of different types, in this post we are going to read the values from our arrays.

Let's work with the following arrays

1. var numbers = [1,2,3,4];
2. var stringArray = new Array("USA", "Canada","China");
3. var objectArray = [{firstName: "Jane", lastName:"Johnson", weight:"115lbs"},{firstName: "Jack", lastName:"Johnson", weight:"200lbs"}];

Let's start with getting a value from an array:

To get the second value of an array you would write the following code by using the :

console.log(numbers[1]);
console.log(stringArray[1]);
console.log(objectArray[1]);