forked from bloominstituteoftechnology/Basic-JavaScript
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy patharrays.js
More file actions
97 lines (89 loc) · 2.68 KB
/
Copy patharrays.js
File metadata and controls
97 lines (89 loc) · 2.68 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
// Complete the following functions.
// These functions only need to work with arrays.
// Do NOT use the built in array methods to solve these. forEach, map, reduce, filter, includes, etc.
// You CAN use concat, push, pop, etc. but do not use the exact method that you are replicating
// You can use the functions that you have already written to help solve the other problems
const each = (elements, cb) => {
for (let i = 0; i < elements.length; i++) {
cb(elements[i], i);
}
// Iterates over a list of elements, yielding each in turn to the `cb` function.
// This only needs to work with arrays.
// based off http://underscorejs.org/#each
};
const reduce = (elements, cb, memo = elements.shift()) => {
// Combine all elements into a single value going from left to right.
// Elements will be passed one by one into `cb`.
// `memo` is the starting value. If `memo` is undefined then make `elements[0]` the initial value.
if (memo === undefined) {
return undefined
}
let acc = memo
for (let i = 0; i < elements.length; i++) {
acc = cb(acc, elements[i], i)
}
return acc
}
const map = (elements, cb) => {
// Produces a new array of values by mapping each value in list through a transformation function (iteratee).
// Return the new array.
return reduce(elements, (acc, v) => {
acc.push(cb(v))
return acc
}, [])
}
const find = (elements, cb) => {
// Look through each value in `elements` and pass each element to `cb`.
// If `cb` returns `true` then return that element.
// Return `undefined` if no elements pass the truth test.
for (let i = 0; i < elements.length; i++) {
if (cb(elements[i])) {
return elements[i]
}
}
return undefined
}
const filter = (elements, cb) => {
// Similar to `find` but you will return an array of all elements that passed the truth test
// Return an empty array if no elements pass the truth test
return reduce(elements, (acc, v) => {
if (cb(v)) {
acc.push(v)
}
return acc
}, [])
}
function isArray(elements) {
return (Object.prototype.toString.call(elements) === '[object Array]')
}
/* Extra Credit */
const flatten = (elements) => {
if (!isArray(elements)) {
return elements
}
while (elements.length === 1 && Array.isArray(elements[0])) {
elements = elements[0]
}
let r = []
r.push(flatten(elements[0]))
let next = elements.slice(1)
while (next.length === 1 && Array.isArray(next[0])) {
next = next[0]
}
if (next.length > 0) {
while (r.length === 1 && Array.isArray(r[0])) {
r = r[0]
}
r = r.concat(flatten(next))
}
return r
}
/* eslint-enable no-unused-vars, max-len */
module.exports = {
each,
map,
reduce,
find,
filter,
flatten
};