2. ECMAScript Overview
What is was originally?
Originally ECMAScript was developed to be a Web Scripting Language which would be used to make a web page more lively by manupulating, customizing and automating the functionalities of the existing system in which it runs.
And as of today...
ECMAScript is an object-oriented programming language for performing computations and manipulating computational objects within a host environment.
In the core of a Web browser is a browser engine and an ECMAScript engine(mostly JavaScript engine) which provides the host environment for execution of the JavaScript code.
For example the Google Chrome browser uses the Blink rendering engine and the V8 JavaScript engine.
By using JavaScript at the client side the client-server architecture has evolved greatly as the computation power could now be distributed on both client and server.
A brief of data-types used in JavaScript(JS)
The various data-types used in JS can be categorized as follows
- The Primitives:
Undefined,Null,Boolean,Number,String - Objects: A collection of properties where each property has attributes that define how the property can be used. These properties can hold primitive values, other objects or functions.
- Functions: JS functions are also objects. They differ from other objects that contain data because functions are callable object, meaning they can be executed or called from other parts of the program.
- Method: It is nothing but a name given to functions that are present as a property of an object.
Special built-in objects
There are some special objects that include the global object, the Object object, the Function object, the Array object, String object, Boolean object, Number object, Math object, Date object, RegExp object, JSON object and some error objects like Error, EvalError, ReferenceError, TypeError, RangeError, SyntaxError and URIError
Operators:
JS includes operators like Unary, Binary, Ternary, Additive, Multiplicative, Bitwise, Relational, Equality, Bitwise Shift, Binary Bitwise, Binary Logical, Assignment and Comma operators.
A few other interesting JS features are which we will experience in detail later on are:
Its syntax is intentionally made similar to Java for ease of use
It is loosely typed language which mean we need not declare the type of a variable during its declaration.
- A function can be called before its declaration appears textually.
a();
function a(){
console.log("Seems to be declared after its called");
}
This works in JS world!!! We will see in detail later why this works.
This was a little bit of overview of JavaScript. In the next post we shall dive into detailed features of the language. Let's start with Objects
References: