参考IIFE内部的功能

Question

I have the following logic:

var first_function = (function(d3, second_function) {
  function third_function(param1, param2) {
    /* do stuff here */
  }
})(d3, second_function);

Outside of an IIFE structure, to access the third function, I could normally do something like:

first_function.third_function(data1, data2);

Where am I going wrong?

Answer 1

If you want to access a property from an IIFE, you need to make that property available by returning an object

var first_function = (function(d3, second_function) {

  // this function is unavailable to the outer scope
  function third_function(param1, param2) {
  /* do stuff here */
  }

  // this object allows us to access part of the inner scope
  // by passing us a reference
  return {
    third_function: third_function
  }
}})(d3, second_function);

Interestingly enough, we can also take advantage of this to create 'private' methods and variables.

var first_function = (function(d3, second_function) {

  // this function is unavailable to the outer scope
  function third_function(param1, param2) {
  /* do stuff here */
  }

  var myPrivate = 0; // outer scope cannot access

  // this object allows us to access part of the inner scope
  // by passing us a reference
  return {
    third_function: third_function,
    getter: function() {
      return myPrivate;   // now it can, through the getter 
    }
  }
}})(d3, second_function);

If you want to learn more about how this works, I suggest you read up on JavaScript scopes and closures.

Answer 2

Its not returning it, so the function is just evaporating. You can do something like this:

var first_function = (function(d3, second_function) {
  function third_function(param1, param2) {
    /* do stuff here */
  }
  return third_function;
})(d3, second_function);

Then, you can access it like this:

first_function( paramForThirdFunc1,paramForThirdFunc2);