Javascript字符串变量没有引用？

Question

I am using the QuickBlox JavaScript API. Looking through their code, I found this line:

var URL_REGEXP = /\b((?:https?:\/\/|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}\/)(?:[^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(?:\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:'".,<>?«»“”‘’]))/gi;

It appears that it has declared a string variable that is a regular expression pattern. Then it goes ahead to use that variable thus:

return str.replace(URL_REGEXP, function(match) {
        url = (/^[a-z]+:/i).test(match) ? match : 'http://' + match;
        url_text = match;
        return '<a href="' + escapeHTML(url) + '" target="_blank">' + escapeHTML(url_text) + '</a>';
    });

I am wondering how is this possible? The var declared in the first line should be a string, but it is unquoted. Shouldn't this be a syntax error?

I went ahead and tested this code on my browser, and it works! This mean's I've got some learning to do here... Can anyone explain how this variable is declared?

Additionally, I tried to run the same code on my friends computer, the Chrome debugger throws a syntax error on the variable declaration line (unexpected token '/'). I am using Chrome Version 36.0.1985.143 m, my friend is using the same thing, but on my computer, it all works fine, on my friends computer, the code stops at the first variable declaration because of "syntax error".

Is there some setting that is different?

Any help would be appreciated.

UPDATE

Thanks for the quick answers. I've come from a PHP background, so thought that all regular expressions has to be initialized as strings :P.

Anyone can reproduce the syntax error I'm getting on my friends computer? (It still happens after disabling all extensions). I can't reproduce it either, and that's what is frustrating me.

UPDATE 2

I have tested and my friends computer and looked through the source. It appear to be due to some encoding problems (I'm not sure what). The regular expression is shown like this:

var URL_REGEXP = /\b((?:https?:\/\/|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}\/)(?:[^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(?:\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:'".,<>?芦禄鈥溾€濃€樷€橾))/gi;

(The characters at the end of the code is some random chinese characters, it seems).

How can I change the encoding to match his browser/system? (He is running on a Windows 7 Chinese simplified system).

Answer 1

It is not a String variable. It is a regular expression .

Calling var varname = /pattern/flags;
is effective to calling var varname = new RegExp("pattern", "flags"); .

You can execute the following in any browser that supports a JavaScript console:

>>> var regex = /(?:[\w-]+\.)+[\w-]+/i
>>> regex.exec("google.com")
... ["google.com"]
>>> regex.exec("www.google.com")
... ["www.google.com"]
>>> regex.exec("ftp://ftp.google.com")
... ["ftp.google.com"]
>>> regex.exec("http://www.google.com")

---

Anyone can reproduce the syntax error I'm getting on my friends computer? (It still happens after disabling all extensions). I can't reproduce it either, and that's what is frustrating me.

According to RegExp - JavaScript documentation :

Regex literals was present in ECMAScript 1st Edition, implemented in JavaScript 1.1. Use an updated browser.

Answer 2

No, it shouldn't be a syntax error. In Javascript, RegExp objects are not strings, they are a distinct class of objects. /.../modifiers is the syntax for a RegExp literal.

I can't explain the syntax error you got on your friend's computer, it looks fine to me. I pasted it into the Javascript console and it was fine.