JavaScript DOM operation forms and styles_Basic knowledge

1 Operation form

f5d188ed2c074f8b944552db028f98a1 tag is the most complex structure in HTML. We can create and generate it through DOM, or operate it through HTMLDOM;

// 使用DOM来创建表格;
 var table = document.createElement('table');
 table.border = 1;
 table.width = 300;

 var caption = document.createElement('caption');
 table.appendChild(caption);
 caption.appendChild(document.createTextNode('人员表'));

 var thead = document.createElement('thead');
 table.appendChild(thead);

 var tr = document.createElement('tr');
 thead.appendChild(tr);

 var th1 = document.createElement('th');
 var th2 = document.createElement('th');

 tr.appendChild(th1);
 th1.appendChild(document.createTextNode('姓名'));
 tr.appendChild(th2);
 th2.appendChild(document.createTextNode('年龄'));

 document.body.appendChild(table);

// The table is complex and has many levels. It will be troublesome to use the previous DOM to obtain a certain element; it is recommended to use HTMLDOM;
Introduction to HTMLDOM properties and methods
Property or method Description
caption holds a reference to the 63bd76834ec05ac1f4c0ebbeaafb0994 element;
tBodies holds an HTMLCollection of 92cee25da80fac49f6fb6eec5fd2c22a elements;
tFoot holds a reference to the 06669983c3badb677f993a8c29d18845 element;
tHead holds a reference to the ae20bdd317918ca68efdc799512a9b39 element;
rows holds an HTMLCollection of a34de1251f0d9fe1e645927f19a896e8 elements;
createTHead() creates the ae20bdd317918ca68efdc799512a9b39 element and returns the reference;
createTFoot() creates the 06669983c3badb677f993a8c29d18845 element and returns the reference;
createCpation() creates the 63bd76834ec05ac1f4c0ebbeaafb0994 element and returns the reference;
deleteTHead() deletes ae20bdd317918ca68efdc799512a9b39 element;
deleteTFoot() deletes the 06669983c3badb677f993a8c29d18845 element;
deleteCaption() deletes the 63bd76834ec05ac1f4c0ebbeaafb0994 element;
deleteRow(pos) deletes the specified row;
insertRow(pos) inserts a row into the specified position in the rows collection;

Attributes and methods added by the92cee25da80fac49f6fb6eec5fd2c22a element
rows holds an HTMLCollection of rows in the 92cee25da80fac49f6fb6eec5fd2c22a element;
deleteRow(pos) deletes the row at the specified position;
insertRow(pos) inserts a row into the specified position in the rows collection;

a34de1251f0d9fe1e645927f19a896e8Attributes and methods added to the element
cells holds the HTMLCollection collection of cells in the a34de1251f0d9fe1e645927f19a896e8 element;
deleteCell(pos) deletes the cell at the specified position;
insertCell(pos) inserts a cell into the specified position of the cells collection and returns a reference;

//HTMLDOM gets the 63bd76834ec05ac1f4c0ebbeaafb0994
of the table alert(table.caption.innerHTML); // Get the content of the caption;

// PS: ae20bdd317918ca68efdc799512a9b39 and 06669983c3badb677f993a8c29d18845 are unique in a table, there can only be one;
// And 92cee25da80fac49f6fb6eec5fd2c22a is not unique, it can be multiple, so that the finally returned ae20bdd317918ca68efdc799512a9b39 and 06669983c3badb677f993a8c29d18845 are element references; and 92cee25da80fac49f6fb6eec5fd2c22a is a collection of elements;

2 Operation Style

As an auxiliary to (X)HTML, CSS can enhance the display effect of the page, but not every browser can support the latest CSS capabilities;
CSS capabilities are closely related to DOM levels, so it is necessary to detect the level of CSS capabilities supported by the current browser;
There are three ways to define styles in HTML:
(1). Use the style attribute to define styles for specific elements;
(2). Use the e5323b80b7cdba5fa628a1c89784fa75 element to define embedded styles;
(3). Contain external style sheet files through the c88766e8e98f17593dff2d30c01c03cf element; 1 // DOM1 level implements the most basic document processing, DOM2 and DOM3 add more interactive capabilities on this basis;
DOM2 adds CSS programming access methods and changing CSS style information;
Detect whether the browser supports DOM1-level CSS capabilities or DOM2-level CSS capabilities
​​​ alert('DOM1 level CSS capability:' document.implementation.hasFeature('CSS','2.0'));
alert('DOM2 level CSS capability:' document.implementation.hasFeature('CSS2','2.0'));

1. Access the style of the element

(1).style property/object
// Any HTML element tag will have a common attribute: style, which will return a CSSStyleDeclaration object;
CSS properties and JavaScript calls
CSS properties JavaScript calls
color style.color
font-size style.fontSize
float style.cssFloat (non-IE)
float style.styleFloat(IE)
var box = document.getElementById('box');
box.style; // CSSStyleDecaration;
box.style.color; box.style.fontSze; // 20px;
// Compatible with IE’s float operation;
Typeof box.style.cssFloat != 'undefined' ? box.style.cssFloat = 'right' : box.style.styleFloat = 'right';

    DOM2级样式规范为style对象定义属性和方法
属性或方法                       说明
cssText                 访问或设置style中的CSS代码;
    box.style.cssText;                      // 获取CSS代码;
    // PS:style属性仅仅只能获取行内的CSS样式,对于另外两种形式内联c9ccee2e6ea535a969eb3f532ad9fe89和链接2cdf5bf648cf2f33323966d7f58a7f3f方法则无法获取到;

(2).计算后的样式:getComputedStyle/currentStyle
// 虽然可以通过style来获取单一值的CSS样式,但对于复合值的样式信息,就需要通过计算样式来获取;
// DOM2级样式,window对象下提供了getComputedStyle()方法:接收两个参数,需要计算的样式元素,和伪类(:hover);如果没有伪类,则null;
// getComputedStyle()方法返回一个CSSStyleDeclaration对象;(与style属性的类型相同);其中包含当前元素的所有计算的样式;
// PS:IE不支持这个DOM2级的方法,但有个类似的属性可以使用currentStyle属性;
var box = document.getElementById('box');
var style = window.getComputedStyle ? window.getComputedStyle(box,null) : null ||box.currentStyle;
alert(style.color); // 颜色在不同的浏览器会有不同rgb()格式;
alert(style.border); // 不同浏览器不同的结果;
alert(sytle.fontFamily); // 计算显示复合的样式值;
// PS:border属性是一个综合属性,所以它在Chrome显示了,Firefox为空,IE为undefined;
// 所以,DOM在获取CSS的时候,最好采用完整写法兼容性最好;比如:border-top-color;

2.操作样式表

// 使用style属性可以设置行内的CSS样式,而通过id和class调用是最常用的方法;
  box.className = 'red';         // 通过className关键字来设置样式;
// 添加多个className函数:
  // 判断是否存在这个class;
  function hasClass(element,className){
    return element.className.match(new RegExp('(\\s|^)'+className+'(\\s|$)'));
  }
  // 添加一个class,如果不存在的话;
  function addClass(element,className){
    if(!hasClass(element,className)){
      element.className += " "+className;
    }
  }
  // 删除一个class,如果存在的话;
  function removeClass(element,className){
    if(hasClass(element,className)){
      element.className = element.className.replace(new RegExp('(\\s|^)'+className+'(\\s|$)'),'');
    }
  }
// 之前使用style属性,仅仅只能获取和设置行内的样式;
// 然后学习的getComputedStyle和currentStyle,只能获取却不能设置;

(1).获得CSSStyleSheet
// CSSStyleSheet类型可以通过2cdf5bf648cf2f33323966d7f58a7f3f元素和c9ccee2e6ea535a969eb3f532ad9fe89元素包含的样式表;
document.implementation.hasFeature('StyleSheet','2.0'); // 是否支持DOM2级样式表;
document.getElementsByTagName('link')[0]; // HTMLLinkElement;
document.getElementsByTagName('style')[0]; // HTMLStyleElement;
// 这两个元素本身返回的是HTMLLinkElement和HTMLStyleElement类型;但CSSStyleSheet类型更加通用一些;
// 得到这个类型非IE使用sheet属性,IE使用styleSheet;
var link = document.getElementsByTagName('link')[0];
var sheet = link.sheet || link.styleSheet; // 得到CSSStyleSheet;

(2).CSSStyleSheet对象的属性和方法
CSSStyleSheet属性或方法
属性或方法 说明
disabled 获取和设置样式表是否被禁用;
href 如果是通过2cdf5bf648cf2f33323966d7f58a7f3f包含的,则样式表为URL,否则为null;
media 样式表支持的所有媒体类型的集合;
ownerNode 指向拥有当前样式表的指针;
parentStyleSheet @import导入的情况下,得到父CSS对象;
title ownerNode中title属性的值;
type 样式表类型字符串;
cssRules 样式表包含样式规则的集合,IE不支持; IE为rules;12 ownerRule @import导入的情况下,指向表示导入的规则,IE不支持;
deleteRule(index) 删除cssRules集合中指定位置的规则,IE不支持;
insertRule(rule,index) 向cssRules集合中指定位置插入rule字符串,IE不支持;

sheet.disabled; // false; 可设置为true;
sheet.href; // css的URL;
sheet.media; // MediaList,集合;
sheet.title; // 得到title属性的值;
sheet.cssRules; // CSSRuleList,样式表规则集合;
sheet.deleteRule(0); // 删除第一个样式规则;
sheet.insertRule("body {background-color:red}",0); // 在第一个位置添加一个样式规则;

// PS:IE中不支持的属性和方法,IE有替代版本;
sheet.rules; // 代替cssRules的IE版本;
sheet.removeRule(0); // 代替deleteRule的IE版本;
sheet.addRule("body","{background-color:red",0); // 代替insertRule的IE版本;

// 除了刚才的方法可以得到CSSStyleSheet类型,还有一种方法是通过document的styleSheets属性来获取;
document.styleSheets; // StyleSheetList,集合;
var sheet = docuemnt.styleSheets[0]; // CSSStyleSheet,第一个样式表对象;

// 添加CSS规则,并兼容所有浏览器函数;
  var sheet = docuemnt.styleSheets[0];
  insertRule(sheet,"body","background-color:red;",0);
  function insertRule(sheet,selectorText,cssText,postion){
    // 如果是非IE;
    if(sheet.insertRule){
      sheet.insertRule(selectorText+"{"+cssText+"}",postion);
    // 如果是IE
    }else if(sheet.addRule){
      sheet.addRule(selectorText,cssText,postion);
    }
  }

(3).CSSRules style sheet rule collection list;
// Through the CSSRules attribute (non-IE) and rules attribute (IE), we can get the rule collection list of the style sheet;
// This way we can perform specific operations on each style;
var sheet = docuemnt.styleSheets[0]; // CSSStyleSheet;
var rules = sheet.cssRules || sheet.rules; // CSSRuleList, a collection list of rules for style sheets;
var rule = rules[0]; // CSSStyleRule, the first rule of the style sheet;
Properties of CSSRules
Property Description
cssText gets the text corresponding to the current overall rule, IE does not support it;
parentRule @import imported, returns rule or null, IE does not support it;
parentStyleSheet The style sheet of the current rule, IE does not support it;
selectorText gets the selector text of the current rule;
style returns a CSSStyleDeclaration object, which can get and set styles;
type represents the constant value of the rule. For style rules, the value is 1, which is not supported by IE;

rule.cssText; // Style text of the current rule;
rule.selectorText; // #box; style selector;
rule.style.color; // red; get the specific style value;
rule.style.backgroundColor = "green"; // Modify the style information of a certain rule;

3 Summary

The DOM2-level style module is mainly developed for operating the style information of elements. Its characteristics are as follows:
(1). Each element has an associated style object, which can be used to determine and modify the in-line style;
(2). To determine the calculated style of an element (including all CSS rules applied to it), you can use the getComputedStyle() method;
(3).IE supports similar methods currentStyle();
(4). Style sheets can be accessed through the document.styleSheets collection; 6 // (5). Style sheet rule collection list CSSRules; 1 // Three methods of operating CSS:

The first style is inline, readable and writable;
The second type of inline/inline and link uses getComputedStyle or currentStyle, which is readable but not writable;
The third type of inlining and connection uses cssRules or rules, which is readable and writable;