JSFiddle - React, Tailwind, and code Playground

by Tran Nguyen

JavaScript

var master = [1, 2, 3, 4, 5, 6, 7, 8, 9];
var sub = [5,6,7];

Array.prototype.arrayContains = function(sub) {
  var first;
  var prev;
  for (var i = 0; i < sub.length; i++) {
    var current = this.indexOf(sub[i]);
    if (current > -1) {
      if (i === 0) {
        first = prev = current;
        continue;
      } else {
        if (++prev === current) {
          continue;
        } else {
          return -1;
        }
      }
    } else {
      return -1;
    }
  }
  return first;
}

alert(master.arrayContains(sub));