javascript 用于检查字符串是否为 a-zA-Z0-9 的正则表达式
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Regular expression for checking if string is a-zA-Z0-9
提问by timpone
I am trying to check if a string is all a-zA-Z0-9but this is not working. Any idea why?
我试图检查一个字符串是否全部，a-zA-Z0-9但这不起作用。知道为什么吗？
var pattern=/^[a-zA-Z0-9]*$/;
var myString='125 jXw'; // this shouldn't be accepted
var matches=pattern.exec(myString);
var matchStatus=1; // say matchStatus is true
if(typeof matches === 'undefined'){
alert('within here');
matchStatus=0; // matchStatus is false
};
if(matchStatus===1){
alert("there was a match");
}
回答by Bergi
exec()returns nullif no match is found, which is typeofobject not undefined.
exec()null如果未找到匹配项，则返回typeof对象 not undefined。
You should use this:
你应该使用这个：
var matches = pattern.exec(myString); // either an array or null
var matchStatus = Boolean(matches);
if (matchStatus)
alert("there was a match");
else
alert('within here');
Or just use the testmethod:
或者只是使用test方法：
var matchStatus = pattern.test(myString); // a boolean
回答by Shaul Hameed
If im not wrong, your regex has no provision for SPACE and your string has space in it. If you want to allow space try this way /^[a-zA-z0-9\ ]*$/
如果我没有错，您的正则表达式没有提供 SPACE 并且您的字符串中有空格。如果你想留出空间试试这种方式 /^[a-zA-z0-9\ ]*$/
回答by Ben McCormick
Try
尝试
if(matches === null){
alert('within here');
matchStatus=0; // matchStatus is false
};
if(matchStatus===1){
alert("there was a match");
}
Regex.exec returns null if there's no match, not undefined. So you need to test that.
如果没有匹配项，则 Regex.exec 返回 null，而不是未定义。所以你需要测试一下。
It seems to work as you expect like that: fiddle
它似乎像你期望的那样工作：fiddle
Documentation for exec: MDN
文档exec：MDN
回答by Krucamper
function KeyString(elm)
{
var pattern = /^[a-zA-Z0-9]*$/;
if( !elm.value.match(pattern))
{
alert("require a-z and 0-9");
elm.value='';
}
}
回答by benqus
I would test it only - in this case:
我只会测试它 - 在这种情况下：
var pattern = /^[a-z0-9]+$/i;
var myString = '125 jXw';
var matchStatus = 1; // say matchStatus is true
if (!pattern.test(matches)) {
matchStatus = 0; // matchStatus is false
};
if(matchStatus === 1){
alert("there was a match");
}
