Accessing Elements

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Accessing Elements

Accessing Elements

Dot Notation

In JavaScript, elements (and other objects) can be referenced using dot notation, starting with the highest-level object (i.e., window). Objects can be referred to by name or id or by their position on the page. For example, if there is a form on the page named "loginform", using dot notation you could refer to the form as follows:

Syntax

window.document.loginform

Assuming that loginform is the first form on the page, you could also refer to it in this way:

Syntax

window.document.forms[0]

A document can have multiple form elements as children. The number in the square brackets ([]) indicates the specific form in question. In programming speak, every document object contains a collection of forms. The length of the collection could be zero (meaning there are no forms on the page) or greater. In JavaScript, collections (and arrays) are zero-based, meaning that the first form on the page is referenced with the number zero (0) as shown in the syntax example above.

Square Bracket Notation

Objects can also be referenced using square bracket notation as shown below:

Syntax

window['document']['loginform']

// and

window['document']['forms'][0]

Dot notation and square bracket notation are completely interchangeable. Dot notation is much more common; however, as we will see later in the course, there are times when it is more convenient to use square bracket notation.

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