ES 2016 and Beyond

These are the notes I prepared for my KeralaJS September 2017 meet talk.

Variables

• Block scope
  You can use let to define block scope variables
• Constants
  Constant variables can be defined with const. Assigning another value to the variables will throw error.

String

• Template literal
  `string${variable}` is the new way to assign strings. variable can be used inside it, rather than using addition operations of string concatenation.
• Multi line strings
• Tag templates
• String.padStart, String.padEnd

Functions

• Map and reduce
• Arrow functions

      function square(num) {
        return num * num;
      }
      square(2);
  

  can be shortened with arrow functions like this

      var square = (num) => num * num;
      square(2);
  

• Scope inside arrow functions
  Arrow functions get the scope of parent. So you no longer have to use bind.
• Default values
  Like other languages, functions can now have default value for the parameters.

      function (fname, lname='') {
          return fname + ' ' + lname;
      }
  

• Spread operator
  Spread operator can be used to expand object or array data.

      let obj = { foo: 'one', bar: 'two' }
      print(...obj);
  

• Rest parameters
  functions can use spread operator to handle remaining parameers.

Objects

• Property shorthand
  You no longer have to specify key if key you want is the same as the variable name.

      let a = 'one';
      let b = 'two';
      let obj = { a, b };
  

• Computed property names
• Method properties
• Destructuring Assignments
• Object.values, Object.entries

Class

• Definition
• Inheritance
• Parent class access

Symbols

• Add
• Size
• Delete

Set

• Add
• Size

Promises

• Resolve
• Reject

Decorators

Async-Await

  getUsers () {
      fetch('/users.html')
        .then(function(user) {
          return response.text()
        })
  };
  
  async getUsers () {
      let response = await fetch('/users.html');
      data = response.text();
      return data;
  }