Magic-API MCP Server

--- title: "Lambda" date: "2022-01-30T10:10:56.000Z" permalink: "/pages/base/lambda/" --- # 映射(map) var list = [ {sex : 0,name : '小明',age : 19}, {sex : 1,name : '小花',age : 18} ]; var getAge = (age) => age > 18 ? '成人' : '未成年' // 利用map函数对list进行过滤 return list.map(item => { age : getAge(item.age), sex : item.sex == 0 ? '男' : '女', name : item.name }); /*结果 [{ "sex": "男", "name": "小明", "age": "成人" },{ "sex": "女", "name": "小花", "age": "未成年" }] */ 等价于以下Linq代码。 return select t.age > 18 ? '成人' : '未成年' age, t.sex == 0 ? '男' : '女' sex, t.name from list t; # 过滤(filter) var list = [ {sex : 0,name : '小明'}, {sex : 1,name : '小花'} ] // 利用map函数对list进行过滤 return list.filter(item => item.sex == 0); // 以上代码可以使用linq代替 return select * from list t where t.sex = 0 /* 结果 [{ "sex": 0, "name": "小明" }] */ # 过滤+映射(filter + map) var list = [ {sex : 0,name : '小明'}, {sex : 1,name : '小花'} ] // 对list进行过滤，然后进行映射 return list.filter(item => item.sex == 0).map(item => { sex : item.sex == 0 ? '男' : '女', name : item.name }); /* 结果 [{ "sex": "男", "name": "小明" }] */ 等价于以下Linq代码。 return select t.sex ==0 ? '男' : '女' sex ,t.name from list t where t.sex = 0 # 分组(group) 默认聚合为List // List<Map<String,Object>> var result = [ { xxx : 1, yyy : 2, value : 11}, { xxx : 1, yyy : 2, value : 22}, { xxx : 2, yyy : 2, value : 33} ]; return result.group(item => item.xxx + '_' + item.yyy) /* Map<Object,List<Object>> { "1_2": [ {"yyy": 2, "xxx": 1, "value": 11}, {"yyy": 2, "xxx": 1, "value": 22} ], "2_2": [{"yyy": 2, "xxx": 2, "value": 33 }] } */ 自定义聚合对象。 return result.group(item => item.xxx + '_' + item.yyy,list => { count : list.size(), sum : list.map(v=>v.value).sum(), avg : list.map(v=>v.value).avg() }) /* Map<Object,Object> { "1_2": { "avg": 16.5, "count": 2, "sum": 33 }, "2_2": { "avg": 33, "count": 1, "sum": 33 } } */ # 关联(join) var year2019 = [ { "pt":2019, "item_code":"code_1", "sum_price":2234 }, { "pt":2019, "item_code":"code_2", "sum_price":234 }, { "pt":2019, "item_code":"code_3", "sum_price":12340 }, { "pt":2019, "item_code":"code_4", "sum_price":2344 } ]; var year2018 = [ { "pt":2018, "item_code":"code_1", "sum_price":1234.0 }, { "pt":2018, "item_code":"code_4", "sum_price":1234.0 } ]; return year2019.join(year2018, (left, right) => left.item_code == right.item_code, (left ,right) => { '年份' : left.pt, '编号' : left.item_code, '今年' : left.sum_price, '去年' : right == null ? 'unknow' : right.sum_price, '环比去年增长' : right == null ? '-': (((left.sum_price - right.sum_price) / right.sum_price * 100) + "%") }); /* [ {"年份": 2019, "今年": 2234, "去年": 1234, "环比去年增长": "81.03728%", "编号": "code_1"}, {"年份": 2019, "今年": 234, "去年": "unknow", "环比去年增长": "-", "编号": "code_2"}, {"年份": 2019, "今年": 12340,"去年": "unknow","环比去年增长": "-","编号": "code_3"}, {"年份": 2019, "今年": 2344, "去年": 1234, "环比去年增长": "89.95138%", "编号": "code_4"} ] */ 等价于以下Linq代码: return select t.pt 年份, t.item_code 编号, t.sum_price 今年, ifnull(t1.sum_price,'unknow') 去年, // ifnull 会对参数进行计算，会报错 所以这里采用三元运算符 t1.sum_price == null ? '-' : ((t.sum_price - t1.sum_price) / t1.sum_price).asPercent(2) 环比去年增长 from year2019 t left join year2018 t1 on t.item_code = t1.item_code