perf: MPE mod lookup with map instead of linear search

[davidlhw]

Context

closes #3674

Implementation

• create a lookup map to access from when comparing module codes, reducing access time to constant instead of linear
• removed moduleCode overwriting as they are already the same

Profiling

tl;dr - using Map to lookup modulecodes is about 50x faster at n=1000 than .find(...)

step 1: generate a large array of random moduleCodes and create a mock fetchedSubmission object and fetchedMpeModuleList object

const n = 10000;

const moduleCodes = Array.from({ length: n }, () =>
  (Math.random() + 1).toString(36).substring(2)
);

const fetchedMpeModuleList = moduleCodes.map((code) => ({ moduleCode: code }));
const fetchedSubmission = {
  preferences: fetchedMpeModuleList.slice(Math.floor(n / 2)),  // half of fetchedMpeModuleList
};

step 2: profile original implementation

console.time("original");
const out1 = fetchedSubmission.preferences.map((preference) => {
  const mpeModule = fetchedMpeModuleList.find(
    (m) => m.moduleCode === preference.moduleCode
  );
  if (!mpeModule) return preference;
  return {
    ...preference,
    test: true,
  };
});
console.timeEnd("original");  // original: 557.182ms
console.log(out1.length);  // 5000

step 3a: profile Map implementation

console.time("map");
const modMap = new Map(
  fetchedMpeModuleList.map((module) => [module.moduleCode, module])
);
const out2 = fetchedSubmission.preferences.map((preference) => {
  if (!modMap.get(preference.moduleCode)) return preference;
  return {
    ...preference,
    test: true,
  };
});
console.timeEnd("map");  // map: 8.299ms
console.log(out2.length);  // 5000

step 3b: profile object implementation

console.time("obj");
const modObj = fetchedMpeModuleList.reduce((lookup, module) => {
  lookup[module.moduleCode] = module;
  return lookup;
}, {});
const out3 = fetchedSubmission.preferences.map((preference) => {
  if (!modObj[preference.moduleCode]) return preference;
  return {
    ...preference,
    test: true,
  };
});
console.timeEnd("obj");  // obj: 8.366ms
console.log(out3.length);  // 5000

Other Information

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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 53.58%. Comparing base (b20b4ce) to head (c888c07).

Files	Patch %	Lines
website/src/views/mpe/form/MpeFormContainer.tsx	0.00%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #3685 +/- ## ========================================== - Coverage 53.61% 53.58% -0.03% ========================================== Files 272 272 Lines 5976 5977 +1 Branches 1428 1428 ========================================== - Hits 3204 3203 -1 - Misses 2772 2774 +2 ```

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[alissayarmantho]

LGTM, nice work at using map instead of find 👍