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The this Object
You may have noticed something strange in the previous example. The
sayName() method references person.name directly, which creates tight coupling between the method and the object. 
This is problematic for a number of reasons. First, if you change the variable name, you also need to
remember to change the reference to that name in the method. Second,
this sort of tight coupling makes it difficult to use the same function for
different objects. Fortunately, JavaScript has a way around this issue.
Every scope in JavaScript has a this object that represents the calling object for the function. 
In the global scope, this represents the
global object (window in web browsers). When a function is called while

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Object Methods
As mentioned in Chapter 1, you can add and remove properties from
objects at any time. When a property value is actually a function, the
property is considered a method. You can add a method to an object in
the same way that you would add a property. For example, in the following code, the person variable is assigned an object literal with a name property and a method called sayName.

var person = {
 name: "Nicholas",
 sayName: function() {
 console.log(person.name);

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Object Methods
As mentioned in Chapter 1, you can add and remove properties from
objects at any time. When a property value is actually a function, the
property is considered a method. You can add a method to an object in
the same way that you would add a property. For example, in the following code, the person variable is assigned an object literal with a name property and a method called sayName.

var person = {
 name: "Nicholas",
 sayName: function() {
 console.log(person.name);

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overloading
Most object-oriented languages support function overloading, which is the
ability of a single function to have multiple signatures. A function signature
is made up of the function name plus the number and type of parameters
the function expects. Thus, a single function can have one signature that
accepts a single string argument and another that accepts two numeric
arguments. The language determines which version of a function to call
based on the arguments that are passed in.
As mentioned previously, JavaScript functions can accept any number
of parameters, and the types of parameters a function takes aren’t speci-

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function sum() {
var result = 0,
i = 0,
len = arguments.length;
while (i < len) {
result += arguments[i];
i++;
}
return result;
}

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const items = new Array();
const now = new Date();
const error = new Error("Something bad happened.");
const func = new Function("console.log('Hi');");
const object = new Object();
const re = new RegExp("\\d+");