Open goldEli opened 4 years ago
<script type="text/javascript">
// 为 button 添加点击事件
// 点击 button 后,button 文字变为红色,再次点击文字还原回绿色
var btn = document.getElementsByTagName('button')[0];
var count = 0;
btn.onclick = function(){
if(count++ %2 == 0){
btn.style.color = "red"
}else{
btn.style.color ="green"
}
}
</script>
<script type="text/javascript"> // 为 button 添加点击事件 // 点击 button 后,button 文字变为红色,再次点击文字还原回绿色 var btn = document.getElementsByTagName('button')[0]; var count = 0; btn.onclick = function(){ if(count++ %2 == 0){ btn.style.color = "red" }else{ btn.style.color ="green" } } </script>
当未来你的 HTML 发生改变,你还需要去修改 js 所以获取 DOM 尽量用 ID
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<button style="color: green" onclick="changeColoe(this)">点击</button>
<script>
// 为 button 添加点击事件
// 点击 button 后,button 文字变为红色,再次点击文字还原回绿色
var i = 0;
var changeColoe = function(obj){
i++;
if((i%2) == 1){
obj.style.color = 'red';
}else{
obj.style.color = 'green';
}
}
</script>
</body>
</html>
<script type="text/javascript"> // 为 button 添加点击事件 // 点击 button 后,button 文字变为红色,再次点击文字还原回绿色 var btn = document.getElementsByTagName('button')[0]; var count = 0; btn.onclick = function(){ if(count++ %2 == 0){ btn.style.color = "red" }else{ btn.style.color ="green" } } </script>
当未来你的 HTML 发生改变,你还需要去修改 js 所以获取 DOM 尽量用 ID
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
#green{
color: green;
}
#red{
color: red;
}
</style>
</head>
<body>
<!-- 方法1 改变style属性
<button style="color: green">点击</button>
<script type="text/javascript">
// 为 button 添加点击事件
// 点击 button 后,button 文字变为红色,再次点击文字还原回绿色
var btn = document.getElementsByTagName('button')[0];
var count = 0;
btn.onclick = function(){
if(count++ %2 == 0){
btn.style.color = "red"
}else{
btn.style.color ="green"
}
} -->
//方法2 改变id属性 改变class属性可以用div.className修改
<button id="green">点击</button>
<script type="text/javascript">
var btn = document.getElementsByTagName('button')[0];
var count = 0;
btn.onclick = function(){
if(count++ %2 == 0){
document.getElementById('green').id = 'red';
}else{
document.getElementById('red').id = 'green';
}
}
</script>
</body>
各司其职
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<button id="btn" style="color: green">点击</button>
<script>
window.onload = function(){
var btn = document.getElementById("btn");
btn.onclick = function(){
var style = window.getComputedStyle(btn, null);
if(style.color == "rgb(0, 128, 0)"){
btn.style.color = "red";
}else{
btn.style.color = "green";
}
}
}
</script>
</body>
</html>
完善以下代码