Over the next few articles, I’m going to break down the new features & syntax of ES6 into bite-size chunks. Please note that some experience writing JS is required to make full uses of these articles.
This is part 1 of many so please keep checking back for the next article in the series.
Part 2 – Template Strings can be found here.
Part 3 – Arrow Functions can be found here.
Part 4 – Classes can be found here.
Currently, to declare a variable in JS the var keyword is used.
var string = 'abc'; var num = 1;
With ES6 come two new keywords which can be used to declare variables. They are const & let.
When a variable is declared using the const keyword, the value assigned should not change. An example of this would be in a user system where once the user is registered, their unique identifier would never change.
const userId = 'somethingUnique';
Once a const is set no changes can be made to it. JS will throw an error if this happens.
When a variable is declared using the let keyword, the value assigned is expected to change. An example of this would be a users password. They may at any time chose to change it.
let userPwd = 'Password123';
Variables declared using let can be changed at any time – it can be used in the say way as the var keyword.
The code is more expressive & easier to read. If you are looking at a large piece of code, it is immediately obvious which variables won’t change and which may change.
Check back shortly for the part 2 – Template Strings.
As not all browsers support ES6 code yet, Babel should be used to transpile (convert) the code into ES5 code.