Implement the chunk array to a given size problem solutions, write tests

Author: somekindofwallflower

06_array_chunking/index.js

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+// --- Directions
+// Given an array and chunk size, divide the array into many subarrays
+// where each subarray is of length size
+// --- Examples
+// chunk([1, 2, 3, 4], 2) --> [[ 1, 2], [3, 4]]
+// chunk([1, 2, 3, 4, 5], 2) --> [[ 1, 2], [3, 4], [5]]
+// chunk([1, 2, 3, 4, 5, 6, 7, 8], 3) --> [[ 1, 2, 3], [4, 5, 6], [7, 8]]
+// chunk([1, 2, 3, 4, 5], 4) --> [[ 1, 2, 3, 4], [5]]
+// chunk([1, 2, 3, 4, 5], 10) --> [[ 1, 2, 3, 4, 5]]
+
+// Steps
+// Create empty array to hold chunks called 'chunked'
+// Loop through each  element in the unchanked array
+// Retrieve the last element in the chunked
+// If element does not exist or the element length is equal to chunk size push e new chunk to the chunked array with the element
+// Else add the element into the chunk
+
+
+// Solution 1
+// function chunk(array, size) {
+//   let chunked = [];
+//   for (let element of array) {
+//       const last = chunked[chunked.length - 1]
+//       if(!last || last.length === size) {
+//           chunked.push([element])
+//       } else {
+//           last.push(element);
+//       }
+//   }
+//     return chunked;
+// }
+
+
+// Steps
+// Create an empty chunk array
+// Create 'index' starts at 0
+// While index is less than array.length
+// Push a slice of length size from array into chunked
+// Add size to index
+
+// Solution 2
+function chunk(array, size) {
+    let chunked = [];
+    let index = 0;
+    for (let el of array) {
+        if(index < array.length) {
+            chunked.push(array.slice(index, index + size))
+            index =  index + size;
+        }
+    }
+    return chunked;
+}
+
+
+module.exports = chunk;

06_array_chunking/test.js

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+const chunk = require('./index');
+
+test('function chunk exists', () => {
+    expect(typeof chunk).toEqual('function');
+});
+
+test('chunk divides an array of 10 elements with chunk size 2', () => {
+    const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+    const chunked = chunk(arr, 2);
+
+    expect(chunked).toEqual([[1, 2], [3, 4], [5, 6], [7, 8], [9, 10]]);
+});
+
+test('chunk divides an array of 3 elements with chunk size 1', () => {
+    const arr = [1, 2, 3];
+    const chunked = chunk(arr, 1);
+
+    expect(chunked).toEqual([[1], [2], [3]]);
+});
+
+test('chunk divides an array of 5 elements with chunk size 3', () => {
+    const arr = [1, 2, 3, 4, 5];
+    const chunked = chunk(arr, 3);
+
+    expect(chunked).toEqual([[1, 2, 3], [4, 5]]);
+});
+
+test('chunk divides an array of 13 elements with chunk size 5', () => {
+    const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13];
+    const chunked = chunk(arr, 5);
+
+    expect(chunked).toEqual([[1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 13]]);
+});