use strict use cases

'use strict'
// restricts undecalred variables
a = 10
function add(){
b= 49
return a+b
}
console.log(add())
// restricts assigning values to read-only properties
const a = 'a'
a= 'b'
function sum(){
return a
}
console.log(sum())
// restricting duplicate parameters
function sumFunc(a,b,b){
return a+b+b
}
console.log(sumFunc(4,6,3))
// restricting eval and arguments as variable Namespace
const eval = 'eval'
const arguments = 'arguments'