Dynamic css using javascript

Using dynamic styling information

The CSS Object Model (CSSOM), part of the DOM, exposes specific interfaces allowing manipulation of a wide amount of information regarding CSS. Initially defined in the DOM Level 2 Style recommendation, these interfaces forms now a specification, CSS Object Model (CSSOM) which aims at superseding it.

In many cases, and where possible, it is best practice to dynamically manipulate classes via the className property since the ultimate appearance of all of the styling hooks can be controlled in a single stylesheet. One’s JavaScript code also becomes cleaner since instead of being dedicated to styling details, it can focus on the overall semantics of each section it is creating or manipulating, leaving the precise style details to the stylesheet. However, there are cases where actually obtaining or manipulating the rules can be useful (whether for whole stylesheets or individual elements), and that is described in further detail below. Note also that, as with individual element’s DOM styles, when speaking of manipulating the stylesheets, this is not actually manipulating the physical document(s), but merely the internal representation of the document.

The basic style object exposes the Stylesheet and the CSSStylesheet interfaces. Those interfaces contain members like insertRule , selectorText , and parentStyleSheet for accessing and manipulating the individual style rules that make up a CSS stylesheet.

To get to the style objects from the document , you can use the Document.styleSheets property and access the individual objects by index (e.g., document.styleSheets[0] is the first stylesheet defined for the document, etc.).

Modify a stylesheet rule with CSSOM

In this example the background of the page is set to red using CSS. The JavaScript then accesses the property using the CSSOM and changes the background to blue.

html lang="en"> head> title>Modifying a stylesheet rule with CSSOMtitle> style> body  background-color: red; > style> script> const stylesheet = document.styleSheets[0]; stylesheet.cssRules[0].style.backgroundColor = "aqua"; script> head> body> The stylesheet declaration for the body's background color is modified via JavaScript. body> html> 

Result

The list of properties available in the DOM from the style property is given on the DOM CSS Properties List page.

To modify styles to a document using CSS syntax, one can insert rules or insert tags whose innerHTML property is set to the desired CSS.

Modify an element’s style

The element style property (see also the section «DOM Style Object» below) can also be used to get and set the styles on an element. However, this property only returns style attributes that have been set in-line (e.g., returns the string » background-color:lightblue «, or directly for that element using element.style.propertyName , even though there may be other styles on the element from a stylesheet).

Also, when you set this property on an element, you override any styles that have been set elsewhere for that element’s particular property you are setting. Setting the border property, for example, will override settings made elsewhere for that element’s border property in the head section, or external style sheets. However, this will not affect any other property declarations for that element’s styles, such as padding or margin or font, for example.

To change a particular element’s style, you can adapt the following example for the element(s) you want to style.

doctype html> html lang="en-US"> head> meta charset="utf-8" /> meta name="viewport" content="width=device-width" /> title>simple style exampletitle> script> function alterStyle(elem)  elem.style.background = "green"; > function resetStyle(elemId)  const elem = document.getElementById(elemId); elem.style.background = "white"; > script> style> #p1  border: solid blue 2px; > style> head> body> p id="p1" onclick="alterStyle(this);"> Click here to change background color. p> button onclick="resetStyle('p1');">Reset background colorbutton> body> html> 

The getComputedStyle() method on the document.defaultView object returns all styles that have actually been computed for an element.

DOM Style Object

The style object represents an individual style statement. The style object is accessed from the document or from the elements to which that style is applied. It represents the in-line styles on a particular element.

Setting style properties

More important than the two properties noted here is the use of the style object to set individual style properties on an element:

doctype html> html lang="en-US"> head> meta charset="utf-8" /> meta name="viewport" content="width=device-width" /> title>Style Property Exampletitle> link rel="StyleSheet" href="example.css" /> script> function setStyle()  document.getElementById("d").style.color = "orange"; > function resetStyle()  document.getElementById("d").style.color = "black"; > script> head> body> div id="d" class="thunder">Thunderdiv> button onclick="setStyle()">Click here to change text colorbutton> button onclick="resetStyle()">Reset text colorbutton> body> html> 

The media and type of the style may or may not be given.

Using the setAttribute method

Note that you can also change style of an element by getting a reference to it and then use its setAttribute method to specify the CSS property and its value.

const el = document.getElementById("some-element"); el.setAttribute("style", "background-color:darkblue;"); 

Be aware, however, that setAttribute removes all other style properties that may already have been defined in the element’s style object. If the some-element element above had an in–line style attribute of say style=»font-size: 18px» , that value would be removed by the use of setAttribute .

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This page was last modified on Jul 7, 2023 by MDN contributors.

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JavaScript for Dynamic CSS Styling: Best Practices and Tips

Learn how to use JavaScript to modify CSS styles dynamically with best practices and tips for optimizing performance. Explore setting CSS properties directly, changing an element’s class attribute, using jQuery’s `css()` method, working with CSS variables, and custom properties.

• Setting CSS Properties Directly
• Changing an Element’s Class Attribute
• JavaScript change CSS properties
• Using jQuery’s css() Method
• Working with CSS Variables and Custom Properties
• Best Practices and Tips for Optimizing Performance
• Other code samples for changing CSS styles with JavaScript
• Conclusion
• How to change CSS style by JS?
• Can JavaScript change HTML styles CSS?
• Can you edit CSS with JS?
• How to dynamically change CSS using JavaScript?

If you’re a web developer, you know that CSS is a fundamental part of web design. CSS allows you to control the visual appearance of your webpage, including layout, typography, and color. However, there may be times when you want to change the appearance of your webpage dynamically based on user input, events, or other factors. That’s where JavaScript comes in.

In this blog post, we will explore the different ways to use JavaScript to modify CSS styles and properties. We will cover setting CSS properties directly, changing an element’s class attribute, and using jQuery’s css() method. We will also discuss how to work with CSS variables and custom properties, and provide best practices and tips for optimizing performance .

Setting CSS Properties Directly

One way to modify CSS styles with JavaScript is to set properties directly. This can be useful when you want to change a specific property of a single element. To do this, you can use the style property of the element’s HTMLElement object.

Here is an example of how to change the color of an element with the ID “elementId” to red:

document.getElementById("elementId").style.color = "red"; 

You can also change other properties, such as font size, background color, and border width.

Changing an Element’s Class Attribute

Another way to modify CSS styles with JavaScript is to change an element’s class attribute. This can be useful when you want to apply a set of styles to multiple elements at once.

To do this, you can use the className property of the element’s HTMLElement object. Here is an example of how to change the class of an element with the ID “elementId” to “newClass»:

document.getElementById("elementId").className = "newClass"; 

You can define the styles for “newClass” in your CSS stylesheet.

JavaScript change CSS properties

Javascript change modify add CSS properties tutorial example explained#javascript #change Duration: 4:57

Using jQuery’s css() Method

If you’re using jQuery in your web project, you can take advantage of the css() method to modify CSS styles. This method allows you to set or return the value of a CSS property for a selected element.

Here is an example of how to change the color of an element with the ID “elementId” to red using jQuery:

You can also use this method to animate changes to CSS properties.

Working with CSS Variables and Custom Properties

CSS variables and custom properties provide a way to define and use reusable values across multiple elements. You can access and modify these properties with JavaScript.

To define a CSS variable, you can use the var() function in your CSS stylesheet. Here is an example of how to define a variable for the main color of your webpage:

To access and modify this variable with JavaScript, you can use the setProperty() method of the CSSStyleDeclaration object. Here is an example of how to change the value of the “–main-color” variable to red:

document.documentElement.style.setProperty("--main-color", "red"); 

Best Practices and Tips for Optimizing Performance

When using JavaScript to modify CSS styles, it’s important to keep best practices in mind to optimize performance. Here are some tips to help you get the most out of your code:

• Use variables to define reusable values.
• Keep styles separate from behavior.
• Minimize the use of inline styles.
• Minimize the use of floats.
• Use shorthand properties.
• Avoid unnecessary specificity.

Here is an example of how to get the value of the “–main-color” variable with JavaScript:

var mainColor = getComputedStyle(document.documentElement).getPropertyValue('--main-color'); 

By following these best practices and tips, you can ensure that your JavaScript code for modifying CSS styles is efficient and effective.

Other code samples for changing CSS styles with JavaScript

In Javascript , for instance, how to change css with js

document.querySelector('h1', container).style.backgroundColor = 'red';

In Javascript , JavaScript HTML DOM — Changing CSS

In Javascript as proof, JavaScript change CSS code sample

document.getElementById('YouDiv').style.marginTop='40px';

In Javascript , for example, Change CSS With Javascript

const thing = document.getElementById("thing"); thing.style.backgroundColor = "blue";

In Javascript , in particular, how to give css style in javascript code example

document.getElementById("myH1").style.color = "red";

In Javascript case in point, Set CSS styles with javascript code example

var style = document.createElement('style'); style.innerHTML = ` #target < color: blueviolet; >`; document.head.appendChild(style);

// Create our shared stylesheet: const sheet = new CSSStyleSheet(); sheet.replaceSync('#target ');// Apply the stylesheet to a document: document.adoptedStyleSheets = [sheet];

In Javascript , for instance, how to change css using javascript code sample

document.getElementById("myText").className = "anyNewClass"

In Javascript , for example, js set css code example

var element = document.createElement('select'); element.style.maxWidth = "100px";

In Javascript , for instance, Set CSS styles with javascript code sample

var style = document.createElement('style'); document.head.appendChild(style); style.sheet.insertRule('#target ');

Conclusion

JavaScript provides web developers with powerful tools for dynamically changing CSS styles and properties. Whether you’re setting CSS properties directly, changing an element’s class attribute, or using jQuery’s css() method, it’s important to keep best practices in mind and optimize for performance. By working with CSS variables and custom properties, developers can create reusable styles that can be modified with JavaScript. With these tips and techniques, you can take your web development skills to the next level.

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