Do DOM tree elements with IDs become global properties?

Javascript Html Dom Global Variables Getelementbyid

Working on an idea for a simple HTMLElement wrapper I stumbled upon the following for Internet Explorer and Chrome:

For a given HTMLElement with an id in the DOM tree, it is possible to retrieve the <div> using its ID as a variable name or as a property of window. So for a <div> like

            
                <div id="example">some text</div>

in Internet Explorer 8 and Chrome you can do:

            
                alert(example.innerHTML); // Alerts "some text".

or

            
                alert(window["example"].innerHTML); // Alerts "some text".

So, does this mean every element in the DOM tree is converted to a property on the global object? And does it also mean one can use this as a replacement for the getElementById method in these browsers?

Understanding DOM Elements with IDs and Global Properties

When you give an element an ID in HTML, it becomes accessible in JavaScript using the `getElementById` method. This method allows you to retrieve the element and manipulate its properties or content.

However, in some browsers like Internet Explorer 8 and Chrome, elements with IDs in the DOM tree are automatically converted to global properties. This means that you can directly access the element using its ID as a variable name or as a property of the `window` object.

Let's take a closer look at how this works.

Example:

Consider the following HTML:

            
                <div id="example">some text</div>

In Internet Explorer 8 and Chrome, you can access the content of the element in two ways:

            
                alert(example.innerHTML); // Alerts "some text".
                alert(window["example"].innerHTML); // Alerts "some text".

Both of these methods retrieve the content of the element with the ID "example".

Are DOM Elements Converted to Global Properties?

No, not every element in the DOM tree is converted to a global property. This behavior is specific to Internet Explorer 8 and Chrome. Other browsers may not support this feature.

Elements with IDs in the DOM tree are automatically assigned as properties on the global `window` object only in Internet Explorer 8 and Chrome.

For example, if you have multiple elements with the same ID, only the first one will be accessible as a global property. Subsequent elements with the same ID will not be available.

It's important to note that this behavior is not recommended or standardized. It is generally considered a bad practice to rely on global variables for accessing elements in the DOM. Instead, it's best to use the `getElementById` method to retrieve the desired element.

Using getElementById Method

The `getElementById` method is the recommended way to access elements in the DOM tree by their IDs.

Here's an example:

            
                const element = document.getElementById("example");
                const content = element.innerHTML;
                alert(content); // Alerts "some text".

Using `getElementById` ensures that your code is more portable and compatible across different browsers.

Additionally, if you have multiple elements with the same ID, `getElementById` will always return the first one, whereas using the global property approach may lead to unexpected results.

Conclusion

In conclusion, elements with IDs in the DOM tree of Internet Explorer 8 and Chrome can be accessed as global properties using their IDs as variable names or properties of the `window` object. However, this behavior is not recommended or standardized.

It's best to use the `getElementById` method to access elements by their IDs. This ensures portability and compatibility across different browsers. Avoid relying on global variables for accessing elements in the DOM, as it can lead to confusion and potential issues in your code.

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