Set 和 Map

1. 数组去重

        <script type="text/javascript">
            [...new Set(array)]
        </script>

2. 条件语句的优化

        <script type="text/javascript">
            // 根据颜色找出对应的水果
            // bad
            function test(color) {
              switch (color) {
                case 'red':
                  return ['apple', 'strawberry'];
                case 'yellow':
                  return ['banana', 'pineapple'];
                case 'purple':
                  return ['grape', 'plum'];
                default:
                  return [];
              }
            }

            test('yellow'); // ['banana', 'pineapple']

            // good
            const fruitColor = {
              red: ['apple', 'strawberry'],
              yellow: ['banana', 'pineapple'],
              purple: ['grape', 'plum']
            };

            function test(color) {
              return fruitColor[color] || [];
            }

            // better
            const fruitColor = new Map()
              .set('red', ['apple', 'strawberry'])
              .set('yellow', ['banana', 'pineapple'])
              .set('purple', ['grape', 'plum']);

            function test(color) {
              return fruitColor.get(color) || [];
            }
        </script>