JavaScript Callback Function.js

// buat object kosong
let _ = {};


// fungsi filter array pada javascript
_.filter = (list, callback) => {
    let storage = [];

    _.each(list, (value, i, list) => {
        if (callback(value, i, list)) storage.push(value);
    })

    return storage

}



// fungsi map pada javascript
_.map = (list, callback) => {
    let storage = [];
    
    //for (let i = 0; i < list.length; i++) {
    //    storage.push(callback(list[i], i, list));
    //}
    
    _.each(list, (value, i, list) => {
        storage.push(callback(value, i, list));
    });
    
    return storage;
}




// buat each untuk menampilkan setiap item pada suatu array 
_.each = (list, callback) => {
    if (Array.isArray(list)) {
        for (let i = 0; i < list.length; i++) {
            callback(list[i], i, list);
        }
    } else {
        for (key in list) {
            callback(list[key], key, list);
        }
    }
}

_.from = arr => {
  return Array.prototype.slice.call(arr);
}



// test
_.each([1, 2, 3, 4, 5, 6, 7, 8], item => console.log(item));

_.filter([1, 2, 3, 4, 5, 6, 7, 8], item => item % 2 === 0);