策略模式粗浅应用

1、策略集中管理（耦合高）： 适合单一功能场景的维护

function Strategy(row) {
  // 配置策略，映射业务
  let rules = {
      a: fna,
      b: fnb,
      c: fnc
    },
    // 配置参数域，如果参数域不一致
    fields = {
      a: 'a',
      b: 'a,b'
    },
    code = row.code,
    field = fields[code],
    action = rules[code],
    args = [row];
  // 参数转成数组形式
  if (field) {
    let keys = field.split(',');
    args = keys.map(function(key) {
      return row[key];
    })
  }

  if (action) action.apply(null, args);
}

2、动态策略模式（低耦合）：适合公共组件或逻辑

/**
  rules:
        code: 策略标识
        action: 策略响应
        fields: 策略参数域
  registor: 注册策略
  run: 执行策略
 **/
let Strategy = {
  rules: {},
  registor(rule) {
    this.rules[rule.code] = rule;
  },
  run(row) {
    let rule = this.rules[row.code];
    if (rule) {
      let field = rule.field,
        args = [row];

      if (field) {
        let fields = field.split(',');

        args = fields.map(function(key) {
          return row[key];
        });
      }
      console.log('args: ', JSON.stringify(args))
      rule.action.apply(null, args);
    }
  }
}

假定的业务逻辑：

function fna(a) {
  console.log(a)
}

function fnb(a, b) {
  console.log(a, b)
}

function fnc({a, b, c}) {
  console.log(a, b, c)
}

// 测试
Strategy.registor({
  code: 'a',
  action: fna,
  field: 'a'
});
Strategy.registor({
  code: 'b',
  action: fnb,
  field: 'a,b'
});
Strategy.registor({
  code: 'c',
  action: fnc
});

let row = {
  a: 'A',
  b: 'B',
  c: 'C',
  d: 'D',
  e: 'E'
};

row.code = 'a';
Strategy.run(row);
row.code = 'b';
Strategy.run(row);
row.code = 'c';
Strategy.run(row);