Commonly used function in my JS project

utils.js

var utils = {
  is: function (instanceOf, data) {
    var dataType = Object.prototype.toString.call(data);
    var expectedType = '[object ' + instanceOf + ']';

    return dataType === expectedType;
  },
  isNot: function (instanceOf, data) {
    return !this.is(instanceOf, data);
  },
  get: function (path, obj) {
    var _this = this;
    var paths = path.split('.');
    var loop = function (o, ks) {
      var k = ks.shift();
      if (!k || _this.isNot('Object', o)) {
        return o;
      } else {
        if (o.hasOwnProperty(k)) {
          return loop(o[k], ks);
        } else {
          return void 0;
        }
      }
    };

    return loop(obj, paths);
  },
  getOr: function (path, defaultVal, obj) {
    return this.get(path, obj) || defaultVal;
  },
  set: function (val, path, obj) {
    var paths = path.split('.');
    var loop = function (o, ks) {
      if (ks.length === 1) {
        var k = ks.pop();
        o[k] = val;
        return o;
      } else {
        var k = ks.shift();
        o[k] = loop({}, ks);
        return o;
      }
    };

    loop(obj, paths);
  },
  partial: function (f) {
    if (this.isNot('Function', f)) {
      var msg = 'First argument should be an instance of function';
      throw new TypeError(msg);
    }

    var args = Array.prototype.slice.call(arguments, 1);
    return function () {
      var argz = Array.prototype.slice.call(arguments);
      return f.apply(this, args.concat(argz));
    }
  },
  curry: function (f) {
    if (this.isNot('Function', f)) {
      var msg = 'Argument should be an instance of function';
      throw new TypeError(msg);
    }

    // TODO
  },
  compose: function () {
    // TODO
  },
};