[Vue.js] Online Goldbach's Conjecture Demo

<div id="vueapp">
  <input v-model="intn" placeholder="Input even integer > 2">
  <p>{{ result }}</p>
</div>

<script src="https://cdn.jsdelivr.net/npm/vue@2.5.16/dist/vue.js"></script>

'use strict';

function SieveOfEratosthenes(n) {
      // Create a boolean array "prime[0..n]" and initialize
      // all entries it as true. A value in prime[i] will
      // finally be false if i is Not a prime, else true.
      var integers = [];
      for (var i = 2; i < n+1; i++) {
              integers[i] = true;
      }

      for (var p = 2; p*p <= n; p++) {
              // If integers[p] is not changed, then it is a prime
              if (integers[p] == true) {
                      // Update all multiples of p
                      for (var i = p * 2; i <= n; i += p) {
                              integers[i] = false;
                      }
              }
      }

      // return all prime numbers <= n
      var primes = [];
      for (var p = 2; p <= n; p++) {
              if (integers[p] == true) {
                      primes.push(p);
              }
      }

      return primes;
}

function Goldbach(n) {
  var primes = SieveOfEratosthenes(n);
  for (var i=0; i < primes.length; i++) {
    var p1 = primes[i];
    var p2 = n - p1;
    if (primes.indexOf(p2) != -1) {
      return [p1, p2];
    }
  }
}

new Vue({
  el: '#vueapp',
  data: {
    intn: 4,
    result: ""
  },
  watch: {
    intn: {
      immediate: true,
      handler(val, oldVal) {
        var n = parseInt(val);
        if (isNaN(n)) {
          this.result = "please input integer";
          return;
        }
        if (n < 3) {
          this.result = "input integer must > 2";
          return;
        }
        if (n%2 == 1) {
          this.result = "input integer must be even";
          return;
        }
        var pp = Goldbach(n);
        this.result = (val + " = " + pp[0] + " + " + pp[1]);
      }
    }
  }
});