let and const were introduced in the ES6 version of Javascript. Which enables the variable shadowing.
Let’s understand more about variable shadowing using an example:
In the above example the variable a is shadowed inside the if block. The value of variable a is temporarily changed inside the if block and that change is only valid inside that block.
Outside the if block the value of variable a is the same old variable that is given in line 5.
Variable Shadowing
- var can be shadowed by let (refer 1 in image below)
- let cannot be shadowed by var , it is called illegal shadowing [throws error : variable already defined] – (refer 2 in the image below)
