is(value).a(Object) ? does('Nijiko').startWith('N') ? does([1,2,3]).endWith(3) ? does({ user: { name: 'Nijiko' } }).contain('user') ?

is.does.js

/**
 * Is / Does
 * 
 * A poetic homage to Ruby.
 * 
 * @author Nijiko Yonskai
 * @license MIT
 */
function is (value) {
  return { 
    a: function (check) {
      if (check.prototype) check = check.prototype.constructor.name;
      var type = Object.prototype.toString.call(value).slice(8, -1).toLowerCase();
      return value !== undefined && value !== null && type === check.toLowerCase();
    },
  };
}

function does (value) {
  var arrayIndexOf = (Array.indexOf ? function (arr, obj, from) { 
    return arr.indexOf(obj, from); 
  } : function (arr, obj, from) {
    var l = arr.length, i = from ? parseInt((1*from) + (from<0 ? l:0), 10) : 0; i = i<0 ? 0 : i;
    for (; i<l; i++) if (i in arr  &&  arr[i] === obj) return i;
    return -1;
  });

  return {
    startWith: function (string) {
      if (is(value).a(String)) return value.slice(0, string.length) == string;
      if (is(value).a(Array)) return value[0] == string;
      return false;
    },

    endWith: function (string) {
      if (is(value).a(String)) return value.slice(-string.length) == string;
      if (is(value).a(Array)) return value[value.length - 1] == string;
      return false;
    },

    contain: function (field) {
      if (is(value).a(String)) return value.indexOf(field) != -1;
      if (is(value).a(Object)) return value.hasOwnProperty(field);
      if (is(value).a(Array)) return !!~arrayIndexOf(value, field);
      return false;
    }
  }
};