Run results for: example-7

Run details:

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:71.0) Gecko/20100101 Firefox/71.0

Browser: Firefox 71

Operating system: Ubuntu

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
multiple loops	260.4 Ops/sec
single loop	279.5 Ops/sec

Script Preparation code:

var records = [];
for (var i = 0; i < 1000; i++) {
  records.push({
    'class': 'Group',
    'groupGUID': `${i}-${i}`,
    'id': i,
  });
  records.push({
    'class': 'test',
  });
}

Tests:

multiple loops
var groupsMapping = records .filter(record => record.class === 'Group') .reduce((collector, record) => { collector[record.groupGUID] = record.id; return collector; }, {});
single loop
var groupsMapping = {}; records .forEach(record => { if (record.class === 'Group') { groupsMapping[record.groupGUID] = record.id; } });

multiple loops

single loop