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// implement map
function map(array, cb) {
let i;
let total = [];
for (i = 0; i < array.length; i += 1) {
total.push(cb(array[i]));
}
return total;
}
// test out the map function
const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
const doubled = map(arr, item => {
return item * 2;
});
console.log(doubled);
// implement filter function
function filter(array, cb) {
let i;
let filtered = [];
for (i = 0; i < array.length; i += 1) {
if (cb(array[i])) {
filtered.push(array[i]);
}
}
return filtered;
}
// test out the filter function
const arr2 = [
{ name: "Bently", age: 2 },
{ name: "Zaphy", age: 12 },
{ name: "Domino", age: 11 }
];
const ageGreaterThanFive = filter(arr2, r => {
return r.age > 5;
});
console.log(ageGreaterThanFive);
/* output
2, 4, 6, 8, 10, 12, 14, 16, 18, 20 ]
[ { name: 'Zaphy', age: 12 }, { name: 'Domino', age: 11 } ]
*/
// implement reduce function
function reduce(array, cb, accumulator) {
let i;
for (i = 0; i < array.length; i += 1) {
if (!accumulator) {
accumulator = array[i];
}
accumulator = cb(accumulator, array[i]);
}
return accumulator;
}
const arr3 = [1, 2, 3, 4];
const arr4 = [
{ key1: "test1", key2: "test2" },
{ key1: "test3", key2: "test4" },
{ key1: "test5", key2: "test6" },
{ key1: "test7", key2: "test8" },
{ key1: "test9", key2: "test10" },
{ key1: "test11", key2: "test12" },
{ key1: "test13", key2: "test14" },
{ key1: "test15", key2: "test16" }
];
// test out the method on simple numbers and objects.
const summed = reduce(arr3, num => {
return 2 * num;
});
console.log(summed);
combinedObjects = reduce(
arr4,
(acc, obj) => {
acc.push(obj.key1);
return acc;
},
[]
);
console.log(combinedObjects);
/* output
[ 'test1',
'test3',
'test5',
'test7',
'test9',
'test11',
'test13',
'test15' ]
*/
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