Callback and Promise

Module1.rb

1.     Array iteration and append its index with the value using callback       
let IterationArray = function(arr){
    let temp = [];
    arr.forEach(function (value, i) {
     let my_hash={}
     my_hash[i] = value 
     temp.push(my_hash);
     });
return temp;
  };
let CallIterateArray = function(arr,callback){
    return callback(arr); 
  };
  console.log(CallIterateArray(["A","B","C","D"],IterationArray));

2. find area and perimeter of the circle using callback
  let Perimeter = function(radius){
return (2Math.PIradius);
};
let Area = function(radius){
return (Math.PIradiusradius);
};
let DoWhatever = function(radius){
console.log('here are your radius $(radius)');
};

let CirclePerimeter = function(radius,callback){
return callback(radius);
};
console.log(CirclePerimeter(5,Perimeter));

console.log(CirclePerimeter(2,Area));
3. setTimeOut function with callback
   let TimeOut = function(string){
    setTimeout(function(){ alert(string); }, 3000);
   };
   
   let CallTimeout = function(name,callback){
    return callback(name); 
  };
  console.log(CallTimeout("Start learning javaScript",TimeOut));

4. find square root of number using promise.

function promiseToCalSquareRoot(num) {
  return new Promise(function (resolve, reject) {
    let sqt = num*num
    if (sqt > 0) {
      resolve(sqt)
    } else {
      reject(sqt)
    }
  });
};

promiseToCalSquareRoot(3).then(function(result) {
  console.log('Success: Square Root is ' + result)
}).catch(function(error) {
  console.log('Please enter a number greater than 0 to cal square root: ' + error)
});