javascript - 查找并计算特定 div 内的所有行

Question

我想查找特定 div 内具有类行的所有 div 的计数

<div class="input_fields_wrap">
    <div class="row"></div>
    <div class="row"></div>
</div>

我尝试过这个，但它不起作用......

var div = document.getElementByClassName('input_field_wrap');
var myrows = div.getElementsByClassName('row');
alert(myrows.length);

Answer 1

使用document#querySelectorAll，并检查作为父选择器子级的行:

var numOfRows = document.querySelectorAll('.input_fields_wrap > .row').length;
console.log(numOfRows);

<div class="input_fields_wrap">
    <div class="row"></div>
    <div class="row"></div>
</div>

---

为什么您的代码不起作用:

//var div = document.getElementByClassName('input_field_wrap');
var div = document.getElementsByClassName('input_fields_wrap'); // typo in getElementsByClassName - missing s in Elements

//var myrows = div.getElementsByClassName('row'); 
var myrows = div[0].getElementsByClassName('row'); // div is an array like object, and you want to get the 1st item

alert(myrows.length);

<div class="input_fields_wrap">
    <div class="row"></div>
    <div class="row"></div>
</div>