Document.getElementById 与 jQuery $()：主要区别是什么？

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

When delving into the realm of web development, understanding the nuances between vanilla JavaScript and jQuery can be crucial. This article examines the subtle differences between two seemingly identical code snippets:

var contents = document.getElementById('contents');

var contents = $('#contents');

Often assumed to be equivalent, their subtle variations can lead to crucial distinctions in their functionality.

Core Differences

• Return Type: document.getElementById('contents') returns an HTML Document Object Model (DOM) object, while $('#contents') returns a jQuery object. jQuery objects possess an array-like structure and support numerous jQuery methods.
• Element Referencing: In jQuery, to access the actual DOM element from a jQuery object, one must specify the index or apply the .get() method, e.g., contents = $('#contents')[0]; or contents = $('#contents').get(0);.

Practical Applications

While both methods serve the same purpose of referencing HTML elements, their variations become apparent in specific scenarios:

• Handling Multiple Elements: jQuery excels in manipulating multiple elements concurrently, e.g., $('.class').hide() hides all elements with the specified class. In contrast, document.querySelectorAll('.class') must be employed to perform a similar task in vanilla JavaScript.
• Cross-Platform Compatibility: jQuery boasts excellent cross-platform compatibility, seamlessly functioning across browsers. document.getElementById, on the other hand, is not guaranteed to work universally.
• Event Handling: jQuery provides an enhanced API for event handling compared to vanilla JavaScript, offering methods like .on(), .toggle(), and .live().

Conclusion

While both document.getElementById and jQuery $() can be used to access elements, their fundamental distinctions in return type and functionality become evident in specific use cases. jQuery's rich API and cross-platform adaptability make it a compelling choice for complex web applications, while vanilla JavaScript remains a viable option for simpler projects.

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