CODEWITHSUNDEEP
javascriptcoffeescript
chenglou
chenglou

Reputation: 3640

CoffeeScript do, pass argument

The following CoffeeScript code: 

do (a) ->
    console.log a

generates this:

(function(a) {
  return console.log(a);
})(a);

How do I pass a value to a like this?

(function(a) {
  return console.log(a);
})("hello");

Upvotes: 13

Views: 7930

Answers (4)

Roger Collins
Roger Collins

Reputation: 1259

If you're using the Module Pattern, this is useful to use the $ global when using multiple Javascript libraries that may conflict with each other:

mySingleton = do ($ = jQuery) -> 
   colorIt -> $('.colorme').css('backgroundColor', 'red')

mySingleton.colorIt()

Upvotes: 3

robkuz
robkuz

Reputation: 9914

you could do this

do (a = "foo")->
    console.log a

But really why would you do this? WHat is the more complete use case you are trying to implement

Upvotes: 2

epidemian
epidemian

Reputation: 19219

do (a = 'hello') ->
  console.log a

Will generate exactly what you want.

Though, i have to admit that i can't see the point of doing that. If you really want a to take the literal value 'hello' inside that scope, then why make another scope? With a being a normal variable declared as a = 'hello' will be enough. Now, if you want to replace a with the value of another variable (that might change in a loop or something) and do do (a = b) -> then i think it makes more sense, but you could simple do do (a) -> and just use a instead of b inside the do scope.

Upvotes: 21

Kyle
Kyle

Reputation: 22258

do is a special keyword in CoffeeScript. It creates a closure. I think you want something like this:

log = (msg) ->
  console.log msg

Compiles to:

var log;

log = function(msg) {
  return console.log(msg);
};

Use it like any other function: log("hello")

Upvotes: 2

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