Run results for: flatMap count vs reduce count

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.1 Safari/605.1.15

Browser: Safari 14

Operating system: Mac OS X 10.15.6

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
reduce with concat	5677115.5 Ops/sec
flatMap	1700665.5 Ops/sec

Script Preparation code:

var arr = [
  {
    loanId: 1077579,
    missingDocs: [
      { docTypeID: 4, docType: "CEMA" },
      { docTypeID: 14, docType: "Policy" },
    ],
  },
  {
    loanId: 1077579,
    missingDocs: [
      { docTypeID: 4, docType: "CEMA" },
      { docTypeID: 14, docType: "Policy" },
    ],
  },
  {
    loanId: 1077579,
    missingDocs: [
      { docTypeID: 4, docType: "CEMA" },
      { docTypeID: 14, docType: "Policy" },
    ],
  },
  {
    loanId: 1077579,
    missingDocs: [
      { docTypeID: 4, docType: "CEMA" },
      { docTypeID: 14, docType: "Policy" },
    ],
  },
  {
    loanId: 1077579,
    missingDocs: [
      { docTypeID: 4, docType: "CEMA" },
      { docTypeID: 14, docType: "Policy" },
    ],
  },
  {
    loanId: 1077579,
    missingDocs: [
      { docTypeID: 4, docType: "CEMA" },
      { docTypeID: 14, docType: "Policy" },
    ],
  },
  {
    loanId: 1077579,
    missingDocs: [
      { docTypeID: 4, docType: "CEMA" },
      { docTypeID: 14, docType: "Policy" },
    ],
  },
  {
    loanId: 1077579,
    missingDocs: [
      { docTypeID: 4, docType: "CEMA" },
      { docTypeID: 14, docType: "Policy" },
    ],
  },
  {
    loanId: 1077579,
    missingDocs: [
      { docTypeID: 4, docType: "CEMA" },
      { docTypeID: 14, docType: "Policy" },
    ],
  },
  {
    loanId: 1077579,
    missingDocs: [
      { docTypeID: 4, docType: "CEMA" },
      { docTypeID: 14, docType: "Policy" },
    ],
  },
  {
    loanId: 1077579,
    missingDocs: [
      { docTypeID: 4, docType: "CEMA" },
      { docTypeID: 14, docType: "Policy" },
    ],
  },
  {
    loanId: 1077579,
    missingDocs: [
      { docTypeID: 4, docType: "CEMA" },
      { docTypeID: 14, docType: "Policy" },
    ],
  },
];

Tests:

reduce with concat
arr.reduce((acc, loan) => acc + loan.missingDocs.length, 0)
flatMap
arr.flatMap(loan => loan.missingDocs).length

Run results for: flatMap count vs reduce count

reduce with concat

flatMap