함수형으로 전환하기 filter, map

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