# 📔 ES6 EcmaScript 6

2 min read, 288 words es6 script es2015 ecmascript2015

List of features in es6 or ECMAScript 2015 (opens new window)
We can easily redeclare a variable. Its a big no no

var counter = 10
// ... some code
var counter = 5

Variables declared outside function could be used inside functions.
However functions declared inside fucntion could not be used outside

# String Concatination

// older syntax
console.log('value = ' + value);

// newer syntax - template delimeters
console.log(`value = ${value}`);

# Object Deconstruction

# Arrow Function

that = this non-sense

Arrow function preserves the references
If you use normal function() {..}, references to this are not preserved
Declare default parametrs with in the arrow function

const user ={
  name: 'Ed',
  age: 25,
  sayName: function() {
    console.log(`My name is ${this.name}`);
    const fullName = () => {
      console.log(`name is ${this.name} and age is ${this.age}`);
    };
    fullName();
  }
}

// practical scenario
button.addEventListner('click', fucntion() {
  this // means button
})

Iterating over List/ Arrays

someList.foreach((item, index) => {
  console.log(`Item = ${item} at index ${index}`);
})

Use map() to transform each element in array inplace

# Array Filters

get only a particular item from list

# Constructor and Classes

generally starts with caps letter
new creates a copy
How to add properties and methods to classes?
ClassName.Prototype.methoName = function() { ... }
call()
class inheritance extends

# Callbacks vs Promises

Variables
String Concatenation
Object Literals
Object Deconstruction
Arrow Functions
Default Parameters
Array Functions
Constructor Functions and Classes
Promise
1. .then
2. .catch

# 📎 References

ECMAScript® 2015 Language Specification (opens new window)

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