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Xiaoqiang's road to HTML5 mobile development (30) - JavaScript review 5

黄舟

Feb 04, 2017 pm 02:25 PM

1. Search

The first way: search based on id

var obj = document.getElementById(id); //document is an instance of HTMLDocument

<html>  
    <head>  
        <script>  
            function f1(){  
                var obj = document.getElementById(&#39;a1&#39;); //双引号，单引号都可以  
                //innerHTML属性：可以访问或者设置节点的html的属性值  
                //alert(obj.innerHTML);   
                obj.innerHTML = "为什么点我"; //双引号单引号都可以  
            }  
            function f2(){  
                var obj = document.getElementById(&#39;d1&#39;);  
                alert(obj.innerHTML);  
            }  
            function f3(){  
                var obj = document.getElementById(&#39;username&#39;);  
                //value属性：可以获取文本输入框的值和改变值  
                alert(obj.value); //获得值  
                obj.value = &#39;abc&#39;;//改变值  
            }  
              
        </script>  
    </head>  
  
    <body style="font-size:30px;font-style:italic;">  
        <!--javascript:; 表示是一个空白的js语句-->  
        <a href="javascript:;" id="a1" onclick="f1();">click me</a><br/>  
        <div id="d1" ><span>你好</span></div><br/>  
        <input type="text" id="username" name="username"/><br/>  
        <input type="button" value="点我吧" onclick="f3();"/>  
    </body>  
</html>

The second way

var arr = node.getElementsByTagName('tagName');

<html>  
    <head>  
        <style>  
            ul{  
                list-style-type:none;     
            }  
            ul li{  
                float:left;  
                border:1px solid black;  
                margin-left:10px;  
                width:100px;  
                height:40px;  
                background-color:red;  
                cursor:pointer;               
            }  
            .selected{  
                background-color:#ff88ee;  
            }  
        </style>  
        <script src="myjs.js"></script>  
        <script>  
            function doAction(index){  
                var arr = $(&#39;u1&#39;).getElementsByTagName(&#39;li&#39;);  
                for(i=0; i<arr.length; i++){  
                    arr[i].className = &#39;&#39;;  
                }  
                var obj = $(&#39;l&#39;+index);  
                obj.className = &#39;selected&#39;;  
            }  
        </script>  
    </head>  
    <body style="font-size:30px;">  
        <ul id="u1">  
            <li onmouseover="doAction(1);" id="l1">选项一</li>  
            <li onmouseover="doAction(2);" id="l2">选项二</li>  
            <li onmouseover="doAction(3);" id="l3">选项三</li>  
        </ul>  
    </body>  
</html>

The third way

Use traversal method (poor browser compatibility)

parentNode

previousSibling previous brother

nextSibling next brother

childNodes All child nodes

firstChild Previous child node

lastChild Next child node

The traversal method is used as little as possible because of browser compatibility issues

2. Create

document.createElement(tagName); //tagName represents the tag name

3. Add

node.appendChild( obj); //Add as the last child

node.insertBefore(obj, refNode); //Add to the front of refNode

node.replaceChild(obj, refNode); //Replace refNode

4. Delete

node.removeChild(obj);

<html>  
    <head>  
        <script src="myjs.js"></script>  
        <script>  
            function f1(){  
                var obj = document.createElement(&#39;div&#39;);      
                obj.innerHTML = &#39;兴趣最重要...&#39;;  
                obj.className = &#39;s1&#39;;  
            //  $(&#39;d1&#39;).appendChild(obj);     
            //  $(&#39;d1&#39;).insertBefore(obj, $(&#39;a1&#39;));   
            //  $(&#39;d1&#39;).replaceChild(obj, $(&#39;a1&#39;));  
                $(&#39;d1&#39;).removeChild($(&#39;a1&#39;));  
            }  
        </script>  
        <style>  
            .s1{  
                width:200px;  
                height:100px;  
                background-color:red;  
            }  
        </style>  
    </head>  
          
    <body style="font-size:30px;" id="d1">  
<!--         <a href="javascript:alert(&#39;hello&#39;);">如何学好java</a>  -->  
        <a id="a1" href="javascript:;" onclick="f1();">如何学好java</a>  
    </body>  
</html>

5. Style

The first way: Modify the className attribute of the node

For example: var obj = document.getElementById('id1'); obj.className = 's1'; //Use s1 style ****See example: form validation*** *

Second method: Modify the style attribute of the node

1. It must be an inline style

2. If the style attribute name to be modified includes "-", For example, background-color, you need to modify node.style.backgroundColor = 'red';

<html>  
    <head>  
        <style>  
            #d1{  
                width:80px;  
                height:80px;  
                background-color:blue;  
                position:relative;  
            }  
        </style>  
        <script src="myjs.js"></script>  
        <script>  
            function f1(){  
                var v1 = parseInt($(&#39;d1&#39;).style.left);  
                $(&#39;d1&#39;).style.left = v1 + 50 + &#39;px&#39;;  
            }  
        </script>  
    </head>  
    <body>  
        <div id="d1" style="left:10px;"></div>  
        <input type="button" value="click me"  
        onclick="f1();"/>  
    </body>  
</html>

How to prohibit the two default behaviors of the browser:

Click the connection, the browser will Send a request to the address pointed to by the href attribute

Click the form submit button, and the browser will submit the form

Prohibited methods

<a href="" onclick="return false;"></a>
<from onsubmint="return false;"></form>

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