JavaScript / TypeScript / ES6 / ReactJS - CheatSheet

js-ts-es6-reactjs.js

Variables & Constants
//-------------------------------------------------------------------------//
|        #        | var | let | const |
|-----------------|-----|-----|-------|
| global scoped   | yes | no  | no    |
| function scoped | yes | yes | yes   |
| block scoped    | no  | yes | yes   |
| redeclarable    | yes | no  | no    |
| reassignable    | yes | yes | no    |
| can be hoisted  | yes | no  | no    |



Declaration / Initilization / Assignment
//-------------------------------------------------------------------------//
// myVar is declared globally
	var myVar = "Hello";
	function myFn(){
		console.log(myVar)
	}
	myFn();
	console.log(myVar);
//-------------------------------------------------------------------------//
// myVar2 is declared inside the function / block
	function myFn2(){
		var myVar2 = "Hello";
		console.log(myVar2)
	}
	myFn2();
	console.log(myVar2); // Uncaught ReferenceError: myVar is not defined
//-------------------------------------------------------------------------//