Detailed explanation of the method of reading and writing CSS styles in native javascript

I encountered this problem recently while studying. In order to facilitate future inquiries, I reviewed some information and summarized the following methods. It is only native JS. If there is something wrong, please point it out! I just hope everyone feels that they have learned something after reading it! The following article mainly introduces the method of using native javascript to read and write CSS styles. Friends in need can refer to it.

Preface

Maybe when you talk about operating css styles, many people will think of jQuery’s css method: $(selector) .css(name) , but have you ever thought about how to use native js to achieve similar functions?

The most familiar method for manipulating styles in native js is the Style object in the DOM. However, this method can only obtain and modify inline styles in html documents, and cannot operate non-inline styles (internal styles and external style sheets).

Through searching and sorting, I summarized the reading and writing implementation of CSS styles using native js. Not much to say below, let’s take a look at the detailed introduction.

Get the style

1. dom style

This method Only inline styles can be obtained:

var text = document.getElementById('text');
var textColor = text.style.color;

// 得到textColor的值为 '#000'

##2. currentStyle

This method is only applicable to IE browsers. It is similar in form to

element.style. The difference is that just like the name of currentStyle - the current style (the style after css is loaded), it returns the current final style of the element. CSS attribute values ​​include styles in internal style tags and externally imported css files.

Usage: element.currentStyle.property

For example, we want to get the width of the box with the id:

##

var boxWidth = document.getElementById('box').currentStyle.width;

// 得到boxWidth的值为 '200px'

3. getComputedStyle

getComputedStyle is a method that can get all the final used CSS property values ​​​​of the current element. What is returned is a CSS style declaration object ([object CSSStyleDeclaration]) and is read-only.

In terms of compatibility, basic support: Chrome, Firfox, IE9, Opera, Safari

Usage: getComputedStyle(element, pseudo-class).Attribute, if the second parameter is not a pseudo-class Set it to null.

var el = document.getElementById("box");
var style = window.getComputedStyle(el , ":after");

Come and encapsulate a general function to get the style

In order to be applicable to all major mainstream Browser, let's write a function:

// 这个函数需要传递两个参数：元素对象和样式属性名称

function getStyle(el, styleName) {

 if( el.currentStyle ) {
 
 // for IE
 return el.currentStyle[styleName];
 
 } else {
 
 // for peace
 return getComputedStyle(el, false)[styleName];
 }
 
}

Then call this function to get the width of the box:

var box = document.getElementById("box");

var boxWidth = getStyle(box, 'width');

This function does not take into account the related operations of pseudo-classes and can be extended as needed~

What is the difference between getComputedStyle and style?
Since they both get the value of the style attribute, what is the difference between them:

Read-only and writable

The getComputedStyle method is read-only and can only get the style but not set it, but

element.style

can both read and write.

The scope of objects obtained

The getComputedStyle method obtains all CSS attribute objects that are ultimately applied to the element (even if there is no CSS code, the default ancestor eight generations will be are displayed); and

element.style

can only get the CSS style in the element's style attribute. Therefore, for a bare element e388a4556c0f65e1904146cc1a846bee, the length attribute value (if any) returned by the getComputedStyle method in the object is 190+ (according to my tests, FF: 192, IE9: 195, Chrome: 253, the results may be different in different environments), And element.style is 0. Quoted from Zhang Xinxu’s blog article

Set the style

1. dom style

Needless to say, this goes without saying, for example, change the background color of the element to red:

var el = document.getElementById('box');
el.style.backgroundColor = 'red';

2. cssText attribute

The essence of cssText is to set the style attribute value of the HTML element. It is a textual representation of a set of style properties and their values. This text is formatted as a CSS stylesheet, with the curly braces surrounding the attribute and value element selectors removed.

Its usage is similar to innerHTML:

document.getElementById("d1").style.cssText = "color:red; font-size:13px;";

For more detailed explanations of how native javascript implements reading and writing CSS styles, please pay attention to the PHP Chinese website for related articles!