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Editorial Team
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Asked: 2026-05-13T10:56:12+00:00

It seems like no matter what input I give this, it always only matches

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It seems like no matter what input I give this, it always only matches 1 character. m.index is always 0 on a match and m.length is always 1. what am I doing wrong here? I have tried it at(and ripped off some code from) http://www.regular-expressions.info/javascriptexample.html and it works as expected there and matches an entire number.

You can see a live example here http://jsbin.com/aqobe

<html>
<head>
<script type="text/javascript">
function __numberBox__correctFormat(text,allow_float){
    var r;
    if(allow_float){
        r=/\$?[\d,\.\W]+/;
    }else{
        r=/\$?[\d,\W]+/;
    }
    var m=r.exec(text);
    if(m==null){
        return false;
    }
        alert(m.index); alert(m.length);

    if(m.index!=0 || m.length!=text.length){ //must match the whole string
        return false;
    }

    return true;
}
</script>
</head>

<body>
Enter your name: <input type="text" id="fname" onchange="
if(__numberBox__correctFormat(this.value,true)){
  alert('tis true');
}else{
  alert('tis false');
}"  />
</body>

</html>

Note I’m wanting for it to accept this input

1234
532,134
$123
493.29
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1 Answer

  1. Editorial Team

    You can use the following code:

    var r;
if(allow_float){
    r=/^\$?\d[\d,\.\W]+$/;
} else {
    r = /^\$?\d[\d,\W]+$/;
}

return r.test(text);

    EDIT: Reject single $.

    The (unescaped) ^ and $ characters match the beginning and of the string, respectively. Therefore, this will only return true if it matches the entire string.

    By the way, your regex is very liberal; it matches strings like $1!2@3#4$5%6^7&8*9(0),.1,.4.

    I recommend using Javascript’s built-in number-parsing methods, like this:

    function __numberBox__correctFormat(text,allowFloat){
    if (text.charAt(0) === '$')
        text = text.substring(1);

    return (allowFloat ? parseFloat : parseInt)(text.replace(',', ''), 10);
}

    Without the ternary cleverness, that would look like this:

    text = text.replace(',', '');
if(allowFloat)
    return parseFloat(text);
return parseInt(text, 10);
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