Simple example of closure in Javascript

function calculate(a,b,cb){

var result = cb(a,b)

console.log(result)

}

function add(a,b){
return a+b;
}
function sub(a,b){
return a-b
}

/* for addition */

calculate(2,3,add)

/* for subtraction */

calculate(3,2,sub)

Javascript Callback with an example

function cal(cb){
/* you can write any operation that takes time here then send the result to callback as given bellow */

console.log(“After exact 1sec you will get hi message”)

setTimeout(function(){

cb(“hi”)
}, 1000)

}
}

cal(function(result){
console.log(result)
})