| JavaScript |
Basics
- Dynamic
- Variables have types but can change from one type to other
- Object Oriented
- Prototypes based
- JIT Complied
- <script> tags to include script
- <script type="text/javascript" href="script1.js"></script>
- Included inside <head> or <body>
- <head> scripts are loaded before DOM
- <body> scripts are loaded during DOM
Variables
- Declaration
- var myVar1
- not necessary to be declared
- myVar2 = "abc";
- "use strict" for enforcing declaration
- Types : typeof(myvariable) to get type
- boolean
- true or false
- number
- 2
- string
- "2"
- object
- var person = {
name="abc",
age=25,
address={street,city,pincode},
function printDetails(){statements;}
}; - objects can be mutated (add new property at any stage)
- person.height=5.5;
- function
- function myFun(var1){
} - undefined
- var var1;
- multiple declaration will overwrite any previous declaration
- Scope
- can be local only inside a function
- will be available for that execution of function and if referred in its subfunctions
Arrays
- var people = [];
- people.push(person1);
- people.length
- if( a == b)
- == or != Types ignored
- === or !== types also need to be equal
- switch(case){case(a) statements;break;case(b) statements;break;}
- condition?true:false
- while(i<10){}
- for(var i = 0; i < people.length ; i++ ){}
- break
- continue
Functions
- functions are another variable type
- cannot be overloaded
- two functions with same name but different parameters will be overwritten as a single function
- function fun1(var1,var2){}
- function calls with variable mismatch works
- fun1(var1) : var2 is undefined
- Anonymous function
- will not have name
- called as and when declared
- function(){}
- functions can be passed as function parameter
- function funMain(var1,callback1){
statements;
callback1();
} - function callback1(){}
- funMain("abc",callback1);
- alert("Message");
- console.log("message")
- logs on debug console window (F12 on browser)
- document
- variable which stores all contents of HTML document
- document.getElementById("idofDOMElement")
- innerHTML
- window
- root of the current window in a browser
- can have document loaded directly of in side multiple frames
- stores all global variables
