함수형으로 전환하기 filter, map

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var users =[         { id:1, name: 'ID', age: 36},         { id:2, name: 'BJ', age: 32},         { id:3, name: 'JM', age: 32},         { id:4, name: 'PJ', age: 27},         { id:5, name: 'HA', age: 25},         { id:6, name: 'JE', age: 26},         { id:7, name: 'JI', age: 31},         { id:8, name: 'MP', age: 23}     ];       //-------------------------------------------------     //30세 이상     var temp_users = [];     for(var i = 0; i < users.length; i++) {         if(users[i].age >= 30) {             temp_users.push(users[i]);         }     }     console.log(temp_users);       //30세 이상 이름     var names = [];     for(var i = 0; i < temp_users.length; i++) {         names.push(temp_users[i].name);     }     console.log(names);       //30세 미만     var temp_users = [];     for(var i = 0; i < users.length; i++) {         if(users[i].age < 30) {             temp_users.push(users[i]);         }     }     console.log(temp_users);       //30세 미만 나이     var ages = [];     for(var i = 0; i < temp_users.length; i++) {         ages.push(temp_users[i].age);     }     console.log(ages);       //-------------------------------------------------     function _filter(list, predi) {         var new_list = [];         for(var i = 0; i < list.length; i++) {             if(predi(list[i])) {                 new_list.push(list[i]);             }         }         return new_list;     }       function _map(list, mapper) {         var new_list = [];         for(var i = 0; i < list.length; i++) {             new_list.push(mapper(list[i]));         }         return new_list;     }         console.log(         _filter(users, function(user) { return user.age >= 30; }));       console.log(         _filter(users, function(user) { return user.age < 30; }));       var over_30 = _filter(users, function(user) { return user.age >= 30; });     console.log(         _map(over_30, function(user) { return user.name; }));       var under_30 = _filter(users, function(user) { return user.age < 30; });     console.log(         _map(under_30, function(user) { return user.age; }));            /*     console.log(         _filter([1, 2, 3, 4], function(num) { return num % 2; }));       console.log(         _filter([1, 2, 3, 4], function(num) { return !(num % 2); }));        */     console.log(         _map(             _filter(users, function(user) { return user.age >= 30; }),             function(user) { return user.name; }));       console.log(         _map(             _filter(users, function(user) { return user.age < 30; }),             function(user) { return user.age; }));                   console.log(         _map(             _filter(users, user => user.age < 30 ),             user => user.name));

 

 

 

 

출처 : www.youtube.com/watch?v=nlde5MeR0nI