Why does my JavaScript regex not work?

Question

I don't understand why, but this code gives me a JavaScript error:

<script type="text/javascript">

String.prototype.format = function(values) {
    var result = this;
    for (var i = 0, len = values.length; i < len; i++) {
        result = result.replace(new RegExp("{" + i + "}", "g"), values[i]);
    }
    return result;
};

alert("Hi {0}, I'm {1}. Are you, {0}?".format(["Chris", "swell"]));

</script>

Error

Exception thrown: invalid quantifier

What's wrong with it?

Just as a side note, you could always use the arguments variable instead of passing an array as a parameter. — alex
– alex, Commented Aug 30, 2010 at 6:29

meder omuraliev · Accepted Answer · 2010-08-30 04:48:45Z

2

I believe you have to escape the { and }.

String.prototype.format = function(values) {
    var result = this;
    for (var i = 0, len = values.length; i < len; i++) {
        result = result.replace(new RegExp("\\{" + i + "\\}", "g"), values[i]);
    }
    return result;
};

answered Aug 30, 2010 at 4:48

meder omuraliev

187k76 gold badges401 silver badges443 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

alex · Accepted Answer · 2010-08-30 04:49:08Z

1

The { and } have special meaning within a regex. They are used to specify exact quantifiers.

To treat them literally, just drop two backslashes before them like so: \\{ and \\}.

One does not work, as I just found out. It must treat one of them as regex delimiters.

answered Aug 30, 2010 at 4:49

alex

492k205 gold badges890 silver badges992 bronze badges

Collectives™ on Stack Overflow

Why does my JavaScript regex not work?

Error

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

Error

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related