What is “define” in RequireJS?

问题:

What is define in RequireJS? Is it a constructor or a function or...?

1. Create module app. Before create module it loads module app2. After initialize callback:

   define(
       'app',
       ['app2'],
       function( app2 ){
           console.log(app2)
       }
   ); 
   

2. What's this syntax?

   define(function (require) {
       var logger = require("./app2");
       console.log(logger);
   });
   

3. And this:

   define({
       color: "black",
       size : "large"
   });
   

回答1:

From the comments:

 The function that handles definitions of modules. Differs from
 require() in that a string for the module should be the first argument,
 and the function to execute after dependencies are loaded should
 return a value to define the module corresponding to the first argument's
 name.

And its signature is:

define = function (name, deps, callback)

In javascript every function is a Function object, so in both cases you are passing to define an object.

//Allow for anonymous modules
if (typeof name !== 'string') {
    //Adjust args appropriately
    callback = deps;
    deps = name;
    name = null;
}