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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+");

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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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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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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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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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The call() Method
The first function method for manipulating this is call(), which executes
the function with a particular this value and with specific parameters.
The first parameter of call() is the value to which this should be equal
when the function is executed. All subsequent parameters are the parameters that should be passed into the function. For example, suppose you
update sayNameForAll() to take a parameter:

function sayNameForAll(label) {
 console.log(label + ":" + this.name);
}

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The apply() Method
The second function method you can use to manipulate this is apply(). The
apply() method works exactly the same as call() except that it accepts only
two parameters: the value for this and an array or array-like object of
parameters to pass to the function (that means you can use an arguments
object as the second parameter). So, instead of individually naming each
parameter using call(), you can easily pass arrays to apply() as the second
argument. Otherwise, call() and apply() behave identically. This example
shows the apply() method in action:

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The bind() Method
The third function method for changing this is bind(). This method was
added in ECMAScript 5, and it behaves quite differently than the other
two. The first argument to bind() is the this value for the new function.
All other arguments represent named parameters that should be permanently set in the new function. You can still pass in any parameters that
aren’t permanently set later.
The following code shows two examples that use bind(). You create
the sayNameForPerson1() function by binding the this value to person1, while
sayNameForPerson2() binds this to person2 and binds the first parameter as
"person2".

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Detecting Properties
Because properties can be added at any time, it’s sometimes necessary to
check whether a property exists in the object. New JavaScript developers
often incorrectly use patterns like the following to detect whether a property exists:

// unreliable
if (person1.age) {
 // do something with age
}