JS Bin// source https://jsbin.com/kiboxat

isHappy.js

/*
    public boolean isHappy(int n) {
        int x = n;
        int y = n;
        while(x>1){
            x = cal(x) ;
            if(x==1) return true ;
            y = cal(cal(y));
            if(y==1) return true ;

            if(x==y) return false;
        }
        return true ;
    }
    public int cal(int n){
        int x = n;
        int s = 0;
        while(x>0){
            s = s+(x%10)*(x%10);
            x = x/10;
        }
        return s ;
    }
*/

'use strict';

function isHappy(n) {
  var x = n;
  var y = n;

  while (x > 1) {
    x = cal(x);
    console.log('x', x);
    if (x === 1) {
      return true;
    }

    y = cal(cal(y));
    console.log('y', y);
    if (y === 1) {
      return true;
    }

    if (x === y) {
      return false;
    }
  }

  return true;
}

function cal(n) {
  var x = n;
  var s = 0;

  while (x > 0) {
    console.log('s 1', s);
    s = s + x % 10 * (x % 10);
    x = Math.floor(x / 10);
    console.log('s 2', s);
  }

  return s;
}

console.log('isHappy(19)', isHappy(19));