How do you add CSS with Javascript?

Question

How do you add CSS rules (eg strong { color: red }) by use of Javascript?

Answer 1

Here's my general-purpose function which parametrizes the CSS selector and rules, and optionally takes in a css filename (case-sensitive) if you wish to add to a particular sheet instead (otherwise, if you don't provide a CSS filename, it will create a new style element and append it to the existing head. It will make at most one new style element and re-use it on future function calls). Works with FF, Chrome, and IE9+ (maybe earlier too, untested).

function addCssRules(selector, rules, /*Optional*/ sheetName) {
    // We want the last sheet so that rules are not overridden.
    var styleSheet = document.styleSheets[document.styleSheets.length - 1];
    if (sheetName) {
        for (var i in document.styleSheets) {
            if (document.styleSheets[i].href && document.styleSheets[i].href.indexOf(sheetName) > -1) {
                styleSheet = document.styleSheets[i];
                break;
            }
        }
    }
    if (typeof styleSheet === 'undefined' || styleSheet === null) {
        var styleElement = document.createElement("style");
        styleElement.type = "text/css";
        document.head.appendChild(styleElement);
        styleSheet = styleElement.sheet;
    }

    if (styleSheet) {
        if (styleSheet.insertRule)
            styleSheet.insertRule(selector + ' {' + rules + '}', styleSheet.cssRules.length);
        else if (styleSheet.addRule)
            styleSheet.addRule(selector, rules);
    }
}

Answer 2

This easy example of add <style> in head of html

var sheet = document.createElement('style');
sheet.innerHTML = "table th{padding-bottom: 0 !important;padding-top: 0 !important;}\n"
+ "table ul {    margin-top: 0 !important;    margin-bottom: 0 !important;}\n"
+ "table td{padding-bottom: 0 !important;padding-top: 0 !important;}\n"
+ ".messages.error{display:none !important;}\n"
+ ".messages.status{display:none !important;} ";

document.body.appendChild(sheet); // append in body
document.head.appendChild(sheet); // append in head

Source Dynamic style - manipulating CSS with JavaScript

Answer 3

Here's a slightly updated version of Chris Herring's solution, taking into account that you can use innerHTML as well instead of a creating a new text node:

function insertCss( code ) {
    var style = document.createElement('style');
    style.type = 'text/css';

    if (style.styleSheet) {
        // IE
        style.styleSheet.cssText = code;
    } else {
        // Other browsers
        style.innerHTML = code;
    }

    document.getElementsByTagName("head")[0].appendChild( style );
}

Answer 4

You can also do this using DOM Level 2 CSS interfaces (MDN):

var sheet = window.document.styleSheets[0];
sheet.insertRule('strong { color: red; }', sheet.cssRules.length);

...on all but (naturally) IE, which uses its own marginally-different wording:

sheet.addRule('strong', 'color: red;', -1);

There is a theoretical advantage in this compared to the createElement-set-innerHTML method, in that you don't have to worry about putting special HTML characters in the innerHTML, but in practice style elements are CDATA in legacy HTML, and ‘<’ and ‘&’ are rarely used in stylesheets anyway.

You do need a stylesheet in place before you can started appending to it like this. That can be any existing active stylesheet: external, embedded or empty, it doesn't matter. If there isn't one, the only standard way to create it at the moment is with createElement.

Answer 5

Here's a sample template to help you get started

Requires 0 libraries and uses only javascript to inject both HTML and CSS.

The function was borrowed from the user @Husky above

Useful if you want to run a tampermonkey script and wanted to add a toggle overlay on a website (e.g. a note app for instance)

// INJECTING THE HTML
document.querySelector('body').innerHTML += '<div id="injection">Hello World</div>';

// CSS INJECTION FUNCTION
//https://stackoverflow.com/questions/707565/how-do-you-add-css-with-javascript
function insertCss( code ) {
    var style = document.createElement('style');
    style.type = 'text/css';
    if (style.styleSheet) {
        // IE
        style.styleSheet.cssText = code;
    } else {
        // Other browsers
        style.innerHTML = code;
    }
    document.getElementsByTagName("head")[0].appendChild( style );
}

// INJECT THE CSS INTO FUNCTION
// Write the css as you normally would... but treat it as strings and concatenate for multilines
insertCss(
  "#injection {color :red; font-size: 30px;}" +
  "body {background-color: lightblue;}"
)

Answer 6

use .css in Jquery like $('strong').css('background','red');

$('strong').css('background','red');

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<strong> Example
</strong>