Can JavaScript Access CSS?

When it comes to web development, JavaScript and CSS are two of the core technologies used. But what if you want to use one to access the other? Can JavaScript access CSS? The answer is yes, but with a few caveats.


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JavaScript can access CSS through the Document Object Model (DOM). The DOM is an interface that allows developers to access and manipulate HTML documents. It provides methods for accessing nodes (which are elements in an HTML document) and their attributes. With these methods, you can write code that can change or add to existing styles in a document.

How Does JavaScript Access CSS?

The primary way that JavaScript accesses CSS is through the getComputedStyle() method. This method takes an element from the DOM and returns its computed style properties. These properties include things like font size, color, width, height, etc. You can then use this information to modify or create additional styles for the element.

For example, let’s say we have a paragraph element with an ID of ‘my-paragraph’. We could use getComputedStyle() to get the font size of this element:

let myParagraph = document.getElementById('my-paragraph'); 
let fontSize = window.getComputedStyle(myParagraph).fontSize; 
console.log(fontSize); // "16px"

We can also modify existing styles with this method. For instance, if we wanted to change the font size of our paragraph, we could do this:

let myParagraph = document.getElementById('my-paragraph'); 
myParagraph.style.fontSize = '24px';

Adding New Styles With JavaScript

The primary limitation of using getComputedStyle() is that it only returns existing styles in a document and cannot add new ones. If you need to add a new style to an element, you will need to use the setAttribute() method instead.

For example, let’s say we wanted to add a border around our paragraph element:

let myParagraph = document.getElementById('my-paragraph'); 
myParagraph.setAttribute("style", "border: 1px solid #000000;");

Conclusion

JavaScript can access CSS through the Document Object Model (DOM). The primary way this is done is through the getComputedStyle() method, which returns existing style properties on an element. To add new styles to an element, you will need to use the setAttribute() method instead.