想问一下问什么首次点击按钮2不能成功变化div2的颜色
1、第一次点击按钮2时不能成功调用函数try2()，点击两次可以调用，其他的时候都正常
2、代码如下：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
#div1{
position: relative;
width: 100px;
height: 100px;
background: black;
border: 1px solid blueviolet;
}
#div2{
position: relative;
width: 100px;
height: 100px;
background:transparent;
border: 1px solid blueviolet;
}
</style>
<script>
function try1(){
var div1=document.getElementById('div1');
var div2=document.getElementById('div2');
if(div1.style.background=='transparent'){
div1.style.background='black';
div2.style.background='transparent';
}else{
div1.style.background='transparent';
div2.style.background='black';
}
}
function try2(){
var div1=document.getElementById('div1');
var div2=document.getElementById('div2');
if(div2.style.background=='transparent'){
div2.style.background='black';
div1.style.background='transparent';
}else{
div2.style.background='transparent';
div1.style.background='black';
}
}
</script>
</head>
<body>
<button onclick="try1()">1</button><div id="div1"></div>
<button onclick="try2()">2</button><div id="div2"></div>
</body>
</html>
div2.style.background获取不到级联样式表中的样式，只能获取到dom style属性中的。js改成下面的，获取级联样式中的背景色，但是注意transparent返回的是rgba格式的
如果不想改js代码，需要给dom直接添加style属性设置background
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
#div1 {
position: relative;
width: 100px;
height: 100px;
background: black;
border: 1px solid blueviolet;
}
#div2 {
position: relative;
width: 100px;
height: 100px;
background: transparent;
border: 1px solid blueviolet;
}
</style>
<script>
function try1() {
var div1 = document.getElementById('div1');
var div2 = document.getElementById('div2');
if (getCss(div1, 'background-color') == 'rgba(0, 0, 0, 0)') {
div1.style.background = 'black';
div2.style.background = 'transparent';
} else {
div1.style.background = 'transparent';
div2.style.background = 'black';
}
}
function try2() {
var div1 = document.getElementById('div1');
var div2 = document.getElementById('div2');
if (getCss(div2, 'background-color') == 'rgba(0, 0, 0, 0)') {
div2.style.background = 'black';
div1.style.background = 'transparent';
} else {
div2.style.background = 'transparent';
div1.style.background = 'black';
}
}
function getCss(el, cssAttr) {
var value = '';
if ( el.currentStyle) {
value = el.currentStyle[cssAttr];
} else if (typeof window.getComputedStyle != 'undefine') {
value = window.getComputedStyle(el, null)[cssAttr];
}
return value;
}
</script>
</head>
<body>
<button onclick="try1()">1</button><div id="div1"></div>
<button onclick="try2()">2</button><div id="div2"></div>
</body>
</html>
你怎么知道没执行，print了吗
我猜div2的初始background既不是transparent也不是black，所以第一次会先走进else里去
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