JavaScript While循环无法正常工作
[英]JavaScript While loop not working
问题描述
I have been trying to develope javascript to recognise a name, display the name, its length and the the letters and what position they appear but i cannot seem to get the while loop to work. 
我一直在尝试开发JavaScript以识别名称，显示名称，名称的长度和字母以及它们出现的位置，但是我似乎无法获得while循环的作用。 could someone please help me out, thanks. 有人可以帮我吗，谢谢。
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html >
<head>
<title>
javascript
</title>
<script>
function displayName(){
var str = prompt("enter your name:");
var len = str.length;
var chara = str.charAt(0);
var n = chara.indexOf(0);
while(chara <= len){
document.write("<br>the letter " + chara + " is number " + n);
chara++;
}
document.write("the name entered is: " + str + "<br></br>" + "the length is " + len);
}
</script>
</head>
<body>
<script>
displayName();
</script>
</body>
</html>
5 个解决方案
解决方案1
1 已采纳 2014-11-14 20:40:19
your loop is using the wrong iterator. 您的循环使用了错误的迭代器。
function displayName(){
var str = prompt("enter your name:");
var len = str.length;
var chara = 0;
while(chara < len){
document.write("<br>the letter " + str.charAt(chara) + " is number " + (chara + 1));
chara++;
}
document.write("<br/>the name entered is: " + str + "<br></br>" + "the length is " + len);
}
解决方案2
1 2014-11-14 20:41:02
You have chara set to the first character, "A" for example. 你必须chara设置为第一个字符，“A”为例。 Then you try to do while A <= 4 (assuming length is 4), which will never be true. 然后，您尝试while A <= 4 （假设长度为4）时执行此操作，这将永远不会成立。 chara needs to be a number for this to work. chara必须是一个数字才能正常工作。
解决方案3
0 2014-11-14 20:39:28
It looks like you're setting chara to the first character of the returned string. 看起来您正在将chara设置为返回字符串的第一个字符。 Try setting it to 0 尝试将其设置为0
var chara = 0;
and see if that works. 看看是否可行。
解决方案4
0 2014-11-14 20:42:38
You are incrementing the wrong variable. 您正在递增错误的变量。 Instead of incrementing chara , you should increment n and reset chara to point to the next character of your string. 而不是增加chara ，您应该增加n并重置chara以指向字符串的下一个字符。 You are also using indexOf improperly - just set n = 0; 您还使用了不正确的indexOf只需设置n = 0; to start with 从开始
解决方案5
0 2014-11-14 20:52:48
Your loop is comparing a character (the first character of the name) to a number (the length of the name). 您的循环正在将一个字符（名称的第一个字符）与一个数字（名称的长度）进行比较。 There are a few ways to approach the task you are trying to accomplish. 有几种方法可以解决您要完成的任务。
If you want to keep using a while loop, you should keep track of a variable that serves as a counter, which counts which iteration of the loop you are on. 如果要继续使用while循环，则应跟踪用作计数器的变量，该变量将对循环进行计数。 This would replace the chara variable. 这将替换chara变量。
here is a live example 这是一个现场的例子
function displayName(){
var str = prompt("enter your name:");
var len = str.length;
var count = 0;
while(count < len){
document.body.innerHTML += "<br>the letter " + str.charAt(count) + " is number " + (count+1);
count++;
}
document.body.innerHTML += "<br>the name entered is: " + str + "<br></br>" + "the length is " + len;
}
I've replaced the calls to document.write() with the innerHTML parameter because it is considered better practice, but you can use either. 我已经用innerHTML参数替换了对document.write()的调用，因为它被认为是更好的做法，但是您可以使用其中任何一个。
As an aside, it would be more semantic to use a for loop for this task. 顺便说一句，对于此任务使用for循环会更具语义。
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