how to make a first-class object in javascript

Question

After reading about the first class object i decided to make my new first-class object like a function but with another name. i searched and found many thing about functions in javascript.

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conclusions from my research

1) that every function is an object and can also be treated like an object.

look here on code:

var myfunc3 = new Function(
                 "a", " return a + 1;");

from page this

as far as i know that any function defined before can be called by using new constructor that is:

    var person = function(name, age){
       this.name=name;
       this.age = age;
}

now i can call this by using new that is:

var x = new person("tom", 34); 

so from the above example i can say that a function defined earlier and then with new can be called again!

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What i don't know

1) how function uses its round brackets,

2) cannot understand the line Function( "a", " return a + 1;");

3) How can we implement function?

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i know you will surely dislike this question but i want to do this because i want to understand every expact of JavaScript.

Thanks!

Answer 1

1) This is the syntax for calling functions, defined in the language.

f(a); // calls the function "f" with the argument "a"

2) Functions are first-class objects, meaning they can be passed around just like any other object and like other objects they have a constructor, Function. The Function constructor creates a new function by evaling the code in a new isolate scope, so you don't have access to the surrounding variables. Again, the Function is a form of eval, avoid it, this is not the way to create functions in JavaScript.

3) You don't implement a function. A function is an object that is already implemented. There are two ways of creating functions in JavaScript. A function declaration:

function f(){}

And a function expression:

var f = function(){};

The difference is about hoisting. See var functionName = function() {} vs function functionName() {}

Answer 2

To answer your question,

1. Round Brackets are Syntax, which holds arguments.

2. It might be a function named Function that accepts two arguments.

3. You can implement a function by using the arguments and doing some logic inside the function and you can also return something using return keyword.

For example:

Function without return:

function Hi(name){
  alert("Hi "+name);
} // Calling it like this: Hi("John"); will alert "Hi John"

And function that returns:

function Hi(name){
  return "Hi "+name;
}// You can store what's returned in a variable like this: var text=Hi("John");alert(text);