document.getElementById() 相當於 Javascript 中的 jQuery $() 嗎？

document.getElementById vs jQuery $(): A Comparative Analysis

A common question arises for web developers: are the following two JavaScript statements equivalent?

<code class="javascript">var contents = document.getElementById('contents');</code>

and

<code class="javascript">var contents = $('#contents');</code>

wherein jQuery is loaded?

Answer: Similarity but Difference

While they appear similar, the answer is not a straightforward yes. Let's delve into the technicalities:

• document.getElementById('contents'): This code returns a HTML DOM Object (Element) representing the first element with the specified ID ('contents') in the document.
• $('#contents'): On the other hand, jQuery's $() function wraps the selection in a jQuery Object. As JavaScript objects are similar to associative arrays, this object stores multiple elements matching the specified selector ('#contents').

Retrieving the Result

To obtain the equivalent result as document.getElementById using jQuery, it is necessary to access the jQuery Object and extract the first element:

<code class="javascript">var contents = $('#contents')[0]; //returns a HTML DOM Object</code>

This code returns the first element in the jQuery Object, which is equivalent to the element returned by document.getElementById.

Practical Implications

While both methods can select elements, they offer different capabilities. document.getElementById provides bare-bones interaction with the DOM, while jQuery provides an extensive range of tools and methods for manipulating the DOM and implementing various effects.

Conclusion

Understanding the distinction between document.getElementById and jQuery's $() is crucial for effective DOM manipulation in web development. By leveraging jQuery's object-oriented approach and rich feature set, developers can efficiently navigate and interact with the DOM.

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