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How Do I Add a Class to an HTML Element Using JavaScript?

How to Add a Class to a Given Element Using JavaScript

To add a class to an existing element, you can utilize several approaches, depending on browser compatibility requirements.

Modern Browsers

For modern browsers, the classList property provides a straightforward solution:

element.classList.add("my-class");

This code will add the "my-class" class to the specified element. To remove a class, use classList.remove.

Internet Explorer 9 and Lower

For older browsers like Internet Explorer 9 and below, you can manually modify the className property:

var d = document.getElementById("div1");
d.className += " otherclass";

Ensure to include a space before the new class name, as this prevents conflicts with existing classes.

Additional Notes

  • The classList property is supported in all major modern browsers, including Chrome, Firefox, Safari, Edge, and Opera.
  • For more information on the classList property and other methods for manipulating classes, refer to the MDN documentation on element.className.

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