The methods of getting elements in JavaScript are: 1. Get elements based on id; 2. Get elements based on tag names; 3. Get elements based on the value of the name attribute; 4. Get elements based on the name of the class style; 5. , Get elements based on the selector.
The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.
1. Get the element based on the id
document.getElementById("value of the id attribute");
2. Get the element based on the tag name
document .getElementsByTagName("The name of the tag");
3. Get the element based on the value of the name attribute
document.getElementsByName("The value of the name attribute");
4 .Get elements based on the name of the class style
document.getElementsByClassName("Name of the class style");
5.Get elements based on the selector
1.document.querySelector ("selector");
2.document.querySelectorAll("selector");
1. Get elements based on id
document.getElementById("id attribute The value of .getElementsByTagName("name of tag");
The return value is a pseudo array
Case: Click the button to change the text content of multiple p tags
<body>
<input type="button" value="弹框" id="btn">
<script>
//根据id属性的值从文档中获取这个元素
var btnobj = document.getElementById("btn"); //为当前的这个按钮元素(对象),注册点击事件,添加事件处理函数(匿名函数)
btnobj.onclick = function () { //响应做的事情
alert("码仙");
};
</script>
</body>3.According to Get the value of the name attribute of the element
document.getElementsByName("the value of the name attribute");
The return value is a pseudo array
Case:Case:Click the button to change The value attribute value in all text boxes whose name attribute value is name1
<body>
<input type="button" value="改变" id="btn">
<p id="dv">
<p>哈哈,我又变帅了</p>
<p>哈哈,我又变帅了</p>
<p>哈哈,我又变帅了</p>
<p>哈哈,我又变帅了</p>
<p>哈哈,我又变帅了</p>
</p>
<script>
//根据id获取按钮,注册点击事件,添加事件处理函数
document.getElementById("btn").onclick = function () {
//根据标签名字获取标签
var pObjs = document.getElementsByTagName("p");
//var pObjs=document.getElementById("dv1").getElementsByTagName("p");
//循环遍历这个数组
for (var i = 0; i < pObjs.length; i++) {
//每个p标签,设置文字
pObjs[i].innerText = "我们都是p";
}
};
</script>
</body>4. Get elements based on the name of the class style document.getElementsByClassName("Name of the class style") ;The return value is a pseudo array
Case: Modify the values of all text boxes
<body>
<input type="button" value="显示效果" id="btn"/><br/>
<input type="text" value="您好" name="name1"/><br/>
<input type="text" value="您好" name="name2"/><br/>
<input type="text" value="您好" name="name1"/><br/>
<input type="text" value="您好" name="name3"/><br/>
<input type="text" value="您好" name="name1"/><br/>
<input type="text" value="您好" name="name1"/><br/>
<script>
//点击按钮,改变所有name属性值为name1的文本框中的value属性值
document.getElementById("btn").onclick = function () {
//通过name属性值获取元素-------表单的标签
var inputs = document.getElementsByName("name1");
for (var i = 0; i < inputs.length; i++) {
inputs[i].value = "我很好";
}
};
</script>
</body>5. Get elements based on the selector
1.document.querySelector( "Selector");The return value is an element objectCase: Click the button pop-up box<body>
<input type="button" value="修改文本框的值" id="btn"/><br/>
<input type="text" value="" class="text"/><br/>
<input type="text" value="" class="text"/><br/>
<input type="text" value="" class="text"/>
<script>
//根据id获取按钮,为按钮注册点击事件,添加事件处理函数
document.getElementById("btn").onclick = function () {
//获取所有的文本框
//根据类样式的名字获取元素
var inputs = document.getElementsByClassName("text");
for (var i = 0; i < inputs.length; i++) {
inputs[i].value = "码仙";
}
};
</script>
</body>2.document.querySelectorAll("Selector");
The return value is a pseudo array
Case: modify the values of all text boxes
<body>
<input type="button" value="显示效果1" id="btn"/>
<input type="button" value="显示效果2" class="btn"/>
<script>
//点击按钮弹出对话框
//根据选择器的方式获取元素
var btnObj1 = document.querySelector("#btn");
btnObj1.onclick = function () {
alert("我变帅了");
};
var btnObj2 = document.querySelector(".btn");
btnObj2.onclick = function () {
alert("哈哈,我又变帅了");
};
</script>
</body>[Recommended learning:
javascript advanced tutorial]
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