????：<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>T全選</title> <style type="text/css"> .box{width: 150px;heig
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>T全選</title>
<style type="text/css">
.box{width: 150px;height: 300px;border: 3px solid #ff6700;border-radius: 5px,padding:5px 10px;margin: 20px auto;}
.box div{border-top: 1px solid #ff6700;padding-top: 10px;margin-bottom: 8px;}
.box input{margin:9px;font-size: 10px;}
span{color:#ff6700;}
</style>
<script type="text/javascript">
function checkall() {
var checkall,tiem;
checkall=document.getElementById('checkall') //獲取全選
item=document.getElementsByName("item[]") //獲取下面的勾選框
console.log(item)
for (var i=0 ; i<item.length; i++) {
if(checkall.checked){
item[i].checked=true; //當(dāng)全選框被選中時(shí)，下面的勾選框選中
}else{
item[i].checked=false; //反之取消選中
}
}
}
</script>
</head>
<body>
<div>
<input type="checkbox" name="item[]"><span>選項(xiàng)1</span><br>
<input type="checkbox" name="item[]"><span>選項(xiàng)2</span><br>
<input type="checkbox" name="item[]"><span>選項(xiàng)3</span><br>
<input type="checkbox" name="item[]"><span>選項(xiàng)4</span><br>
<input type="checkbox" name="item[]"><span>選項(xiàng)5</span><br>
<input type="checkbox" name="item[]"><span>選項(xiàng)6</span><br>
<input type="checkbox" name="item[]"><span>選項(xiàng)7</span><br>
<input type="checkbox" name="item[]"><span>選項(xiàng)8</span><br>
<div>
<input type="checkbox" id="checkall" onclick="checkall()" name=""><label for="checkall">全選</label>
</div>
</div>
</body>
</html>
總結(jié)：
for (var i=0 ; i<item.length; i++)｛｝
本來(lái)for里面第2個(gè)參數(shù)，結(jié)束長(zhǎng)度里為什么放length有點(diǎn)懵逼，然后console.log(item)后發(fā)現(xiàn)取出的數(shù)據(jù)里，有個(gè)length長(zhǎng)度（這里應(yīng)該是個(gè)數(shù)）有幾個(gè)item。然后item[] 后面的[]是數(shù)組下標(biāo)預(yù)留的放括號(hào)？
?? ???：滅絕師太?? ??：2018-12-17 09:27:52
???? ??：表示變量item獲取的是一個(gè)數(shù)組對(duì)象??！其實(shí)不理解的測(cè)試測(cè)試就明白了，繼續(xù)加油！