Run results for: Symbol vs String property access speed

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.0.0 Safari/537.36

Browser: Chrome 138

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

String read

156K/s

Symbol overwrite prototype

144K/s

Symbol read prototype

143K/s

String overwrite prototype

140K/s

Symbol write

137K/s

String read prototype

129K/s

Symbol read

14K/s

String overwrite

14K/s

Symbol overwrite

14K/s

String write

14K/s

View exact numbers

Test name	Executions per second
✓ String read	156,087 Ops/sec
Symbol overwrite prototype	143,723 Ops/sec
Symbol read prototype	143,245 Ops/sec
String overwrite prototype	139,815 Ops/sec
Symbol write	137,071 Ops/sec
String read prototype	129,474 Ops/sec
Symbol read	14,147 Ops/sec
String overwrite	14,033 Ops/sec
Symbol overwrite	13,982 Ops/sec
String write	13,784 Ops/sec

Script Preparation code:

var strings = [];
var symbols = [];
var stringMap = {__proto__: null};
var symbolMap = {__proto__: null};
var emptyMap = {__proto__: null};
for (let i = 0; i < 1000; i++) {
  strings[i] = `foobar${i}`;
  symbols[i] = Symbol(`foobar${i}`);
  stringMap[strings[i]] = i;
  symbolMap[symbols[i]] = i;
}
var stringProtoMap = {__proto__: stringMap};
var symbolProtoMap = {__proto__: symbolMap};
function mapRead(map, keys) {
  let total = 0;
  for (const key of keys) {
    total += map[key];
  }
  return total;
}
function mapWrite(map, keys) {
  for (const key of keys) {
    map[key] = true;
  }
}

Tests:

Symbol read
mapRead(symbolMap, symbols)
Symbol read prototype
mapRead(symbolProtoMap, symbols);
Symbol write
mapWrite(emptyMap, symbols);
Symbol overwrite
mapWrite(symbolMap, symbols);
Symbol overwrite prototype
mapWrite(symbolProtoMap, symbols);
String read
mapRead(stringMap, strings);
String read prototype
mapRead(stringProtoMap, strings);
String write
mapWrite(stringMap, strings);
String overwrite
mapWrite(stringMap, strings);
String overwrite prototype
mapWrite(stringProtoMap, strings);