var vs let vs const
var:
- hoisted (always declared at top of scope, global if none)
- function scope
let:
- block scope
- not redeclarable
const:
- block scope
- not reassignable
- not redeclarable
Note: Although it may seem like these hold only semantic meaning, using the
appropriate keywords helps the JS engines' compiler to decide on what to optimize.js var vs const
//var variables can be re-declared and updated
var greeter = "hey hi";
var greeter = "say Hello instead";
//it becomes a problem when you do not realize that a variable
//greeter has already been defined before.
//const declarations are block scoped
//const cannot be updated or re-declared
const greeting = "say Hi";
greeting = "say Hello instead";// error: Assignment to constant variable.
const greeting = "say Hi";
const greeting = "say Hello instead";// error: Identifier 'greeting' has already been declaredCopyright © 2021 Codeinu
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