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JavaScript DOM Scripting By Example Improving the Application Code Refactor 2: Readable Branching Logic

I don't understand how to use the '[]' and when to use it.

Can somebody please explain this to me please? Thank You

Jeff Muday
Jeff Muday
Treehouse Moderator 28,720 Points

The '[]' connotes an empty list (or array) in JavaScript. It is usually used to initialize an array but can be used anytime you need to start a empty (blank) array or reset an list.

let myArray = [];

2 Answers

Hi Jonathan!

[] just initializes an empty array.

Like this:

let myArr = [];

And then you can add elements like this:

myArr.push('itemOne');
myArr.psuh('itemTwo');
myArr.push('itemThree');

You can also do it this way:

var myArr = new Array();

And there are pros/cons of each approach.

This explains in way more detail than I ever could:

https://stackoverflow.com/questions/931872/what-s-the-difference-between-array-and-while-declaring-a-javascript-ar

I hope that helps.

Stay safe and happy coding!

Grace Marsh
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.a{fill-rule:evenodd;}techdegree seal-36
Grace Marsh
Front End Web Development Techdegree Graduate 16,665 Points

Hi Jonathan,

In addition to being used for arrays, I thought that perhaps this excerpt from a Treehouse question may assist you with how square brackets are used: Given this code:

 function createElement( elementName, property, value ){
     const element = document.createElement(elementName);   
     element[property] = value;
}

The brackets dynamically access the property of element using the string contained in property.