Map.getOrInsert() Benchmark

Chrome 143 ships Map.prototype.getOrInsert() and getOrInsertComputed(). This benchmark compares the new insert-if-missing helpers with two classic counter patterns over 50,000 random words and reports min, median, and max time across 5 runs.

Checking for Map.prototype.getOrInsert…

Benchmark Runner

50,000 random words × 5 runs each. Min / median / max shown for each pattern.

1. Classic has/get/set

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ms median
min — · max —

2. get-or-default

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ms median
min — · max —

3. getOrInsert()

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ms median
min — · max —

Implementation Reference

// Pattern 1: Classic has/get/set const map = new Map(); for (const word of words) { if (map.has(word)) { map.set(word, map.get(word) + 1); } else { map.set(word, 1); } }
// Pattern 2: Get-or-default (nullish coalescing) const map = new Map(); for (const word of words) { map.set(word, (map.get(word) ?? 0) + 1); }
// Pattern 3: Map.prototype.getOrInsert() — Chrome 143 // getOrInsert(key, value) // returns the existing value or inserts and returns the default. const map = new Map(); for (const word of words) { map.set(word, map.getOrInsert(word, 0) + 1); } // getOrInsertComputed(key, factory) lazily creates defaults: const groups = new Map(); for (const word of words) { groups.getOrInsertComputed(word[0], () => []).push(word); } // Polyfill used on browsers without the native methods: if (typeof Map.prototype.getOrInsert !== 'function') { Map.prototype.getOrInsert = function(key, value) { if (this.has(key)) return this.get(key); this.set(key, value); return value; }; } if (typeof Map.prototype.getOrInsertComputed !== 'function') { Map.prototype.getOrInsertComputed = function(key, factory) { if (this.has(key)) return this.get(key); const value = factory(key); this.set(key, value); return value; }; }

Use-case Presets

Each preset runs one of the shipped get-or-insert helpers on a distinct real-world use case.

Word Frequency

Count occurrences of each word across a corpus with getOrInsert.

Click Run to execute.

Event Counter

Track per-event-type counts from a stream of 10,000 browser events.

Click Run to execute.

Nested Map Builder

Build a Map<category, Map<key, count>> and lazily create each inner Map.

Click Run to execute.

see also