grantit.js

/**
 * You are given two non-empty arrays `a` and `b`, each consisting of objects of
 * type Entry (see the type declaration below)
 * Each 'label' is unique within an array (e.g. you cannot have two entries
 * with `label` 'a' within the same array).
 *
 * Write a function `merge` which does the following:
 *   1) Merges the contents of the two arrays together and returns a new array.
 *     When two entries have the same `label`, the result should have
 *     their `value` property summed up.
 *
 *     Each `label` must remain unique within the resulting array.
 *     E.g. { label: 'a', value: 1 } and { label: 'a', value: 2 }
 *     should be combined into { label: 'a', value: 3 }
 *
 *   2) Sorts the resulting array by the `label` property in ascending order
 *     (you can use standard JS string comparison)
 *
 *     For example:
 *      [
 *       { label: 'Abc', value: 1 },
 *       { label: 'b', value: 1 },
 *       { label: 'a', value: 1 }
 *      ]
 *      should become
 *      [
 *       { label: 'Abc', value: 1 },
 *       { label: 'a', value: 1 },
 *       { label: 'b', value: 1 }
 *      ]
 *
 * To simplify the solition, you can assume the following:
 *  - Both arrays length 1 =< length <= 10000
 *  - `label` is a non-empty string consinsting of letters of English alphabet (a-z A-Z)
 *  - `value` is a non-negative number (value >= 0)
 *  - The order of elements' `labels` within the array is random (see example)
 *  - Each 'label' is unique within an array (you cannot have two entries
 *    with `label` 'a' within the same array).
 *
 *  For any questions & submissions - please send an email to develop@grantit.io
 *
 *  Requirements for submission:
 *   - Please specify your name in the email subject
 *   - Attach your submission. You can make a .txt / .js file attachment to your email
 *     or provide a link to a public codesandbox / codepen / replit / codeshare.
 *
 *  If your code has several iterations - feel free to leave all of them within
 *  the same file. That will help us to understand your thought process better.
 */

type Entry = {
  label: string;
  value: number;
};

const merge = (array1: Entry[], array2: Entry[]): Entry[] => {
  const entriesMapByLabel: {[key: string]: number} = {};
  
  for (let {label, value} of [...array1, ...array2]) {
    entriesMapByLabel[label] = entriesMapByLabel[label] && entriesMapByLabel[label] + value || value;
  }
  
  const mergedEntries: Entry[] = Object.keys(entriesMapByLabel).map(key => ({label: key, value: entriesMapByLabel[key]}));
  mergedEntries.sort(entriesCompareFunction)
  
  return mergedEntries
};

function entriesCompareFunction(a: Entry, b: Entry): number {
  const [label1, label2]: Array<string> = [a.label, b.label]
  if (label1 < label2) return -1
  if (label2 < label1) return 1
  return 0
}

// /** Use the following code to test your submission.

const a: Entry[] = [
  {label: 'a', value: 1},
  {label: 'b', value: 1},
  {label: 'c', value: 1},
  {label: 'e', value: 5},
];
const b: Entry[] = [
  {label: 'Abc', value: 100},
  {label: 'e', value: 0},
  {label: 'a', value: 2},
  {label: 'c', value: 1},
  {label: 'd', value: 1},
];


const result = merge(a, b);
console.log(result);

// console.log('A' < 'a')

// The result should be
// [
//  { label: 'Abc', value: 100 },
//  { label: 'a', value: 3 },
//  { label: 'b', value: 1 },
//  { label: 'c', value: 2 },
//  { label: 'd', value: 1 },
//  { label: 'e', value: 5 },
// ]
// */