With the introduction of EcmaScript 6 (EcmaScript 2015), 2 new keywords(among a lot of other language features) are added:
- const: creates a read-only reference to a value. It does not mean the value it holds is immutable, just that the variable identifier cannot be reassigned.
- let: declares a block scope local variable
ES6 Conventions:— Reginald Braithwaite (@raganwald) February 9, 2015
1. use const by default.
2. use let if you have to rebind a variable.
3. use var to signal untouched legacy code.
Here are some general rules that I follow:
- If a variable won’t be reassigned I use ‘const’
- If a variable may be reassigned I use ‘let’
- If someone points a gun at my head and I have no other choice, I use ‘var’