When i started with Javascript, i would not understand as to why is it considered so special as compared to other languages and what is it that makes it different.
Certain things i found interesting, u might as well :)
First thing to Note... Everything in Javascript is an Object, or atleast derived from an object.
Primitives in Javascript are String, Number, Boolean, Null and undefined.
1. Functions
Functions in javascript are different because they can take any form. What i mean by this is functions are objects i.e they are called function objects. Other differences are functions can be passed as a parameter, it can be returned just like any other variables, that is reason why they are called the first class citizens. (Higher order functions)
2. Hoisting
What is hoisting? As the name suggest hoisting means raising something (like hoisting a flag [:P]).
Ok, enough of ENGLISH meanings , lets get back to Javascript.
In JavaScript all the variables are hoisted to top, i.e all the declarations only are hoisted not its assignment. below with example.
Program 1:
console.log(a);
var a= 10;
In Program 1 the value of `a` would be undefined, it will not throw an error as compared to other languages, reason being "Hoisting".
After hoisting the Program 1 would look something like this:
var a;
console.log(a);
a=10;
So, the declarations of a is taken to the top and not its assignment.
All the variables declared are by default set the value of undefined.
You can try the above example or various other examples to make this concept clear.
3. Scopes
Scope means up to where a particular variable would be available in a program/script.
Scopes belong to global scope, function scope. Lets understand each one and how they work.
a. Global scope: Is the one that is not inside any function or in short it starts with the first line of the code.
b. Function scope: This scope starts with the function and ends with the last ending brace. Variables inside the function are not accessible outside are called the local variables.
There is something more to this... The Closures ... lets unsderstand this with an example.
function a() {
var alocal = 10;
function b() {
// variable alocal is accessible here
console.log(alocal) // will print 10.
}
}
Inner function has access to its outer function, thats why it can access the variable alocal.
4. "This" Scope
By default this points to the outermost global scope i.e window.
The scope of "this" changes depending on the way it is called.
In a function the "this" points to the global scope
function a() {
//this = global scope
}
Similarly function inside a function also points to a global scope.
function b() {
function c() {
// this still points to the global scope
}
}
Only incase of objects its different.
var objLocal = {
loc : 1,
func: function() {
console.log("this", this); // this points to object scope and not global
}
}
We could change the scopes using .call() , .apply() methods
This is just the start, many more things to explore.. will post more in the coming blogs.
Thats all in this blog FOLKS!!
This is just the start, many more things to explore.. will post more in the coming blogs.
Thats all in this blog FOLKS!!
