Generate Key Map Object Javascript
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- Get Keys Javascript Object
- Generate Key Map Object Javascript Code
- Generate Key Map Object Javascript Download
- Generate Key Map Object Javascript Pdf
Real Life Objects, Properties, and Methods
In real life, a car is an object.
- Create an empty div element above the script element and give it an id of 'map'. This is where your map will be displayed. Create a script element in the head of your page and put function called initMap inside it. Create a mapOptions object and set values for the properties you want to modify.
- Converting a JSON Text to a JavaScript Object. A common use of JSON is to read data from a web server, and display the data in a web page. For simplicity, this can be demonstrated using a string as input. First, create a JavaScript string containing JSON syntax.
A car has properties like weight and color, and methods like start and stop:
| Object | Properties | Methods |
|---|---|---|
car.name = Fiat car.model = 500 car.weight = 850kg car.color = white | car.start() car.drive() car.brake() car.stop() |
All cars have the same properties, but the property values differ from car to car.
All cars have the same methods, but the methods are performed at different times.
JavaScript Objects
You have already learned that JavaScript variables are containers for data values.
This code assigns a simple value (Fiat) to a variable named car:
Objects are variables too. But objects can contain many values.
This code assigns many values (Fiat, 500, white) to a variable named car:
The values are written as name:value pairs (name and value separated by a colon).
JavaScript objects are containers for named values called properties or methods.
Object Definition
You define (and create) a JavaScript object with an object literal:
Example
Spaces and line breaks are not important. An object definition can span multiple lines:
Example
firstName: 'John',
lastName: 'Doe',
age: 50,
eyeColor: 'blue'
};
Object Properties
The name:values pairs in JavaScript objects are called properties: Cisco 3560 generate rsa key.
| Property | Property Value |
|---|---|
| firstName | John |
| lastName | Doe |
| age | 50 |
| eyeColor | blue |
Accessing Object Properties
You can access object properties in two ways:
or
Example1
Try it Yourself »Example2
Try it Yourself »Object Methods
Objects can also have methods.
Methods are actions that can be performed on objects.
Methods are stored in properties as function definitions.
| Property | Property Value |
|---|---|
| firstName | John |
| lastName | Doe |
| age | 50 |
| eyeColor | blue |
| fullName | function() {return this.firstName + ' ' + this.lastName;} |
A method is a function stored as a property.
Example
firstName: 'John',
lastName : 'Doe',
id : 5566,
fullName : function() {
return this.firstName + ' ' + this.lastName;
}
};
The this Keyword
In a function definition, this refers to the 'owner' of the function.
In the example above, this is the person object that 'owns' the fullName function.
In other words, this.firstName means the firstName property of this object.
Read more about the this keyword at JS this Keyword.
Accessing Object Methods
You access an object method with the following syntax:
Example
Try it Yourself »If you access a method without the () parentheses, it will return the function definition:
Example
Try it Yourself »Do Not Declare Strings, Numbers, and Booleans as Objects!
When a JavaScript variable is declared with the keyword 'new', the variable is created as an object:
var y = new Number(); // Declares y as a Number object
var z = new Boolean(); // Declares z as a Boolean object
Avoid String, Number, and Boolean objects. They complicate your code and slow down execution speed.
You will learn more about objects later in this tutorial.
- TypeScript Tutorial
- TypeScript Useful Resources
- Selected Reading
An object is an instance which contains set of key value pairs. The values can be scalar values or functions or even array of other objects. The syntax is given below −
Syntax
As shown above, an object can contain scalar values, functions and structures like arrays and tuples.
Get Keys Javascript Object
Example: Object Literal Notation
On compiling, it will generate the same code in JavaScript.
The output of the above code is as follows −
TypeScript Type Template
Let’s say you created an object literal in JavaScript as −
In case you want to add some value to an object, JavaScript allows you to make the necessary modification. Suppose we need to add a function to the person object later this is the way you can do this.
If you use the same code in Typescript the compiler gives an error. This is because in Typescript, concrete objects should have a type template. Objects in Typescript must be an instance of a particular type.
You can solve this by using a method template in declaration.
Example: Typescript Type template
On compiling, it will generate the same code in JavaScript.
The output of the above code is as follows −
Objects can also be passed as parameters to function.
Example: Objects as function parameters
The example declares an object literal. The function expression is invoked passing person object.
On compiling, it will generate following JavaScript code.
Its output is as follows −
You can create and pass an anonymous object on the fly.
Example: Anonymous Object
Generate Key Map Object Javascript Code
On compiling, it will generate following JavaScript code.
Its output is as follows −
Duck-typing
In duck-typing, two objects are considered to be of the same type if both share the same set of properties. Duck-typing verifies the presence of certain properties in the objects, rather than their actual type, to check their suitability. The concept is generally explained by the following phrase −
Generate Key Map Object Javascript Download
“When I see a bird that walks like a duck and swims like a duck and quacks like a duck, I call that bird a duck.”
Generate Key Map Object Javascript Pdf
The TypeScript compiler implements the duck-typing system that allows object creation on the fly while keeping type safety. The following example shows how we can pass objects that don’t explicitly implement an interface but contain all of the required members to a function.