idx/lib/idx.test.js

Utility function for traversing properties on objects and arrays.

/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @format
 */

'use strict';

// eslint-disable-line strict
jest.unmock('./idx');
var idx = require('./idx');
describe('idx', function () {
  it('returns properties that exist', function () {
    var a = {
      b: {
        c: 123
      }
    };
    expect(idx(a, function (_) {
      return _.b.c;
    })).toEqual(123);
  });
  it('throws non-"property access" errors', function () {
    var error = new Error('Expected error.');
    var a = {};
    Object.defineProperty(a, 'b', {
      get: function get() {
        throw error;
      }
    });
    expect(function () {
      return idx(a, function (_) {
        return _.b.c;
      });
    }).toThrow(error);
  });
  it('throws a `TypeError` when calling non-methods', function () {
    var a = {
      b: 'I am a string'
    };
    expect(function () {
      return idx(a, function (_) {
        return _.b();
      });
    }).toThrow(new TypeError('_.b is not a function'));
  });
  it('returns null for intermediate null properties', function () {
    var a = {
      b: null
    };
    expect(idx(a, function (_) {
      return _.b.c;
    })).toEqual(null);
  });
  it('returns undefined for intermediate undefined properties', function () {
    var a = {
      b: undefined
    };
    expect(idx(a, function (_) {
      return _.b.c;
    })).toEqual(undefined);
  });
  it('returns undefined for intermediate undefined array indexes', function () {
    var a = {
      b: []
    };
    expect(idx(a, function (_) {
      return _.b[0].c;
    })).toEqual(undefined);
  });
  it('returns null for error in capital case', function () {
    var error = new TypeError('b is NULL');
    var a = {};
    Object.defineProperty(a, 'b', {
      get: function get() {
        throw error;
      }
    });
    expect(idx(a, function (_) {
      return _.b.c;
    })).toEqual(null);
  });
  it('returns undefined for error in capital case', function () {
    var error = new TypeError('b is UNDEFINED');
    var a = {};
    Object.defineProperty(a, 'b', {
      get: function get() {
        throw error;
      }
    });
    expect(idx(a, function (_) {
      return _.b.c;
    })).toEqual(undefined);
  });
});