for循环在第一次迭代时停止

Question

EDIT Thank you all for your assistance. 编辑谢谢大家的帮助。 I have made the modifications to the script, with try and catch (err), however, i still do not get the alert when the code is run. 我已经使用try and catch（err）对脚本进行了修改，但是，当代码运行时，我仍然没有收到警报。 I've also replaced "studentInfo[i].getElementsByTagName("id")[i].childNodes[i].nodeValue" with "studentInfo[i].getElementsByTagName("id")[0].childNodes[0].nodeValue" as well as all similar references, except now, it won't even return the first loop. 我还将“ studentInfo [i] .getElementsByTagName（“ id”）[i] .childNodes [i] .nodeValue”替换为“ studentInfo [i] .getElementsByTagName（“ id”）[0] .childNodes [0]。 nodeValue”以及所有类似的引用，但现在除外，它甚至不会返回第一个循环。 It seems to be exiting the function before it hits "catch" for some reason.I've marked the changes in bold. 由于某种原因，它似乎在退出“ catch”之前就退出了。我已将更改标记为粗体。

I know this has been posted quite a bit on this site, but none of the answers seem to quite be able to help me. 我知道这已经在该网站上发布了很多，但是似乎没有任何答案可以帮助我。 I have a for loop that stops iterating after the first loop. 我有一个for循环，在第一个循环后停止迭代。 The data from the first loop is correct, but I need it to keep looping through. 来自第一个循环的数据是正确的，但是我需要它来不断循环。 I've used a couple different lint tools and they say my code is valid, so I must be forcing it to exit the loop some how. 我使用了几个不同的lint工具，他们说我的代码有效，因此我必须强制其退出循环。 Someone help me figure out what I'm doing wrong, please. 请有人帮我弄清楚我在做什么错。

  <html>
  <head>
  <title>Tardy Reporting</title>
  <script type="text/javascript" src="students.js">
  </script>
  </head>
  <body>

  <h1>Scan in Student ID</h1>
  <form method="POST" name="idForm" id="idForm" />
    <input type="text" name="idNumber" id="idNumber"/>
    <input type="button" name="Search" value="Search"  onClick="getId(document.idForm.idNumber.value);" />
  </form>
  <br></br>
  <div id="div1"></div>
  <p>
  </body>
  </html>

var ajxObj;
  if(window.XMLHttpRequest){
    ajxObj = new XMLHttpRequest();
  }
  else{
    ajxObj = new ActiveXObject('Microsoft.XMLHTTP');
  }  
ajxObj.open("GET","studentbase.xml",false);
ajxObj.send();
xmlData = ajxObj.responseXML;
var studentInfo = xmlData.getElementsByTagName("student");

function getId(studentId) {
  **try{**
    for(var i = 0; i < studentInfo.length; i++) {
        if(studentId == **studentInfo[i].getElementsByTagName("id")[0].childNodes[0].nodeValue || studentId === studentInfo[i].getElementsByTagName("name")[0].childNodes[0].nodeValue**){
            document.getElementById('div1').innerHTML=(studentInfo[i].getElementsByTagName("name")[0].childNodes[0].nodeValue);
        }
        else {
        document.getElementById('div1').innerHTML="Error: Not Found"
        }
    }
   **}catch (err){
      alert(err.ToString());
    }**

} }

<?xml version="1.0" encoding="UTF-8" ?>

<thebase>
    <student>
    <id>50011234</id>   
        <name>Mike Simpson</name>
        <grade>n/a</grade>
        <teacher>George Washington</teacher>
        <tardies>0</tardies>
    </student>
    <student>
        <id>50012345</id>
        <name>Greg Pollard</name>
        <grade>n/a</grade>
        <teacher>Darth Vadar</teacher>
        <tardies>0</tardies>
    </student>
    <student>
        <id>50013456</id>
        <name>Jason Vigil</name>
        <grade>n/a</grade>
        <teacher>Obi Wan Kenobi </teacher>
        <tardies>0</tardies>   
    </student>
</thebase>

Answer 1

I suspect your code is throwing an error and you are not aware of this. 我怀疑您的代码抛出错误，并且您不知道这一点。 I suspect the reference "studentInfo[i].getElementsByTagName("id")[i].childNodes[i].nodeValue" should be "studentInfo[i].getElementsByTagName("id")[0].childNodes[0].nodeValue". 我怀疑引用“ studentInfo [i] .getElementsByTagName（“ id”）[i] .childNodes [i] .nodeValue”应为“ studentInfo [i] .getElementsByTagName（“ id”）[0] .childNodes [0]。 nodeValue”。

Try putting a "try...catch" around the "for" loop, like so: 尝试在“ for”循环中放置“ try ... catch”，如下所示：

function getId(studentId) {
    try {
        for(var i = 0; i < studentInfo.length; i++) {
            if (studentId == studentInfo[i].getElementsByTagName("id")[i].childNodes[i].nodeValue || studentId === studentInfo[i].getElementsByTagName("name")[i].childNodes[i].nodeValue){
                document.getElementById('div1').innerHTML=(studentInfo[i].getElementsByTagName("name")[0].childNodes[0].nodeValue);
            }
            else {
            document.getElementById('div1').innerHTML="Error: Not Found"
            }
        }
    } catch (err) {
        alert(err.ToString());
    }
}

Answer 2

if语句中必须有三个等号（即“ ===”）。

for循环在第一次迭代时停止

问题描述

2 个解决方案

解决方案1
3 已采纳 2012-02-13 23:11:22

解决方案2
0 2012-02-14 15:20:29

for循环在第一次迭代时停止

问题描述

2 个解决方案

解决方案1 3 已采纳 2012-02-13 23:11:22

解决方案2 0 2012-02-14 15:20:29

解决方案1
3 已采纳 2012-02-13 23:11:22

解决方案2
0 2012-02-14 15:20:29