javascript + coffeescript，具有分组运算符？

Question

Is there grouping operator for coffeescript? I'm trying to turn this:

var urlParams;
(window.onpopstate = function () {
    var match,
        pl     = /\+/g,  // Regex for replacing addition symbol with a space
        search = /([^&=]+)=?([^&]*)/g,
        decode = function (s) { return decodeURIComponent(s.replace(pl, " ")); },
        query  = window.location.search.substring(1);

    urlParams = {};
    while (match = search.exec(query))
       urlParams[decode(match[1])] = decode(match[2]);
})();

into coffeescript. I have this so far, but I'm not getting it correct

window.onpopstate = ->
  pl     = /\+/g  # Regex for replacing addition symbol with a space
  search = /([^&=]+)=?([^&]*)/g
  decode = (s) ->
    return decodeURIComponent(s.replace(pl, " "))
  query  = window.location.search.substring(1)

  urlParams = {};
  while (match = search.exec(query))
    urlParams[decode(match[1])] = decode(match[2]);

Trying to alert, but getting urlParams is not defined

jQuery ->
  alert(urlParams['hair'])

It might be because of the () at the end of the function that I'm not getting it?

Answer 1

CoffeeScript will declare variables in the scope at their first assignment. Since you first assign urlParams within onpopstate , that's where it's declared, and is not accessible outside there. To replicate the JavaScript's behavior, you've got to initialize it outside of the onpopstate handler:

urlParams = null
window.onpopstate = ->
  # ...

Note that this assumes that urlParams will only be accessed within that one script; since CoffeeScript wraps everything in an IIFE and urlParams will be trapped inside it, you cannot access it outside if declared that way. If you want it to be truly global, accessible from other scripts as well, you'll need to replace every occurrence with window.urlParams .

A few other things, though:

1. The () at the end of the JavaScript version is indeed not there in the CoffeeScript version, although that's not what caused your problem. Fortunately, there's a very easy way to do this in CoffeeScript without adding a bunch of parentheses: use do :

    do window.onpopstate = -> # ... 

2. Trailing semicolons are not required in CoffeeScript. I'd remove them.

3. That return in the definition of decode is implicit in CoffeeScript. I'd remove it.

4. Parentheses are not required around the condition of the while . I'd remove them.

5. If you'd like, you can take advantage of CoffeeScript's implicit function calls without parentheses, eg:

    while match = search.exec query 

   There's several other places you could apply this too, although for readability's sake I'd only do it where it seems sensible.