# ECMAScript

# Support

• tutorialspoint-es6

# The Basic

• Dynamic Typing
  • JavaScript is an un-typed language
  • a JavaScript variable can hold a value of any data type
  • The value type of a variable can change during the execution of a program and JavaScript takes care of it automatically
  • Strong constrain type, view TypeScirpt

• Variable Scope
  • Global Scope : can be accessed from within any part of the JavaScript code
  • Local Scope : can be accessed from within a function where it is declared

• Variable hoisting
  • variables will be initialized to undefined by default
  • JavaScript runtime will scan for variable declarations and put them to the top of the function or script

# Basic Operators

• 2 + 3 Here in the expression, 2 and 3 are operands and the symbol + (plus) is the operator
• Arithmetic + ++ - -- * % /
• Relational > < == >= <= !=
• Logical && || !
• Bitwise & | ^ ~ << >> >>>
• Assignment = += -= *= /=
• typeof
• Spread ... converts an array into individual array elements

# about loop

• for...in loop through an object's properties

var obj = {a:1, b:2, c:3};

for (var prop in obj) {
   console.log(obj[prop]); // 1 2 3
}

• for…of iterate iterables instead of object literals

for (let val of[12 , 13 , 123]){
   console.log(val) // 12 13 123
}