【angular2】@angular/cdk/keycodes 学习02

1. cdk 文档 https://material.angular.io/cdk/categories

2. keycodes 模块提供

• import {
      hasModifierKey
  } from "@angular/cdk/keycodes";

（1）判断是否有 "修饰按键" 按下(type ModifierKey = 'altKey' | 'shiftKey' | 'ctrlKey' | 'metaKey';)

• it('should check whether the alt key is pressed', () => {
      const event = createKeyboardEvent('keydown', 0);
      const altEvent = createKeyboardEvent('keydown', 0, '',  {alt: true});
  
      expect(hasModifierKey(event)).toBe(false);
      expect(hasModifierKey(altEvent)).toBe(true);
    });

（2）https://github.com/angular/components/blob/master/src/cdk/keycodes/keycodes.ts