JavaScript - 如果语句使用.offsetHeight不起作用

Question

我是JavaScript新手，正在练习。我试图显示具有类名“test”的div内的h1和p元素的组合高度。我查了各种各样的东西，觉得我真的很接近，但无法完成这个工作。任何人都可以帮忙？

HTML：

<div class="test"> 
    <h1>Understanding Scope</h1> 
    <p>By understanding code's <em>scope</em>, we know when that code affects only one part of our code, or the entire codebase. If we create things that are <em>global</em> in scope, we are giving any code the supreme power to control our code. So we want to protect our code by being very careful when creating things that are global in scope. This is especially important if you plan on using JavaScript libraries like jQuery.</p> 
</div> 
<h1>Local Scope</h1> 
<p>JavaScript uses <em>function scope</em>, meaning every time we create a new function the scope changes. Any code inside that function is <em>local</em> to that function. Code that is local in scope is not accessible to outside code.</p> 

的JavaScript：

function testing(){ 
    if (document.getElementsByClass('test')){ 
     var headerHeight = document.getElementsByTagName('h1').offsetHeight; 
     var textHeight = document.getElementsByTagName('p').offsetHeight; 
     var totalHeight = headerHeight + textHeight; 

     alert(totalHeight); 
    } 
} 

testing(); 

Answer 1

这是document.getElementsByClassName，不getElementsByClass，H1和P标签还你得到阵列

function testing(){ 
    if (document.getElementsByClassName('test')){ 
     var headerHeight = document.getElementsByTagName('h1')[0].offsetHeight; 
     var textHeight = document.getElementsByTagName('p')[0].offsetHeight; 
     var totalHeight = headerHeight + textHeight; 

     alert(totalHeight); 
    } 
} 

testing(); 

Answer 2

function testing(){ 
    if (document.getElementsByClassName('test')){ 

     var headerHeight = document.getElementsByTagName('h1')[0].offsetHeight; 
     var textHeight = document.getElementsByTagName('p')[0].offsetHeight; 
     var totalHeight = headerHeight + textHeight; 

     alert(totalHeight); 
    } 
} 

testing（）;