performance

High-resolution time measurement API. Provides now(), timeOrigin, and mark()/measure() for performance profiling.

Global

Global	Type	Description
performance	Performance	Time measurement interface

performance.now()

Returns a high-resolution timestamp in milliseconds (with microsecond precision) relative to the runtime start.

let start = performance.now();

// ... do work ...

let elapsed = performance.now() - start;
console.log(`Operation took ${elapsed.toFixed(3)}ms`);

The returned value is a DOMHighResTimeStamp (double-precision float). It's relative to performance.timeOrigin.

performance.timeOrigin

The Unix timestamp (ms) when the qzjs runtime was created.

let now = performance.timeOrigin + performance.now();
// Equivalent to Date.now()

performance.mark(name)

Record a named timestamp:

performance.mark('start-work');

// ... do work ...

performance.mark('end-work');

performance.measure(name, startMark?, endMark?)

Measure the duration between two marks:

performance.mark('a');
// ... work ...
performance.mark('b');

let measure = performance.measure('work', 'a', 'b');
console.log('Duration:', measure.duration, 'ms');

// Without marks: measures since timeOrigin
let fullTime = performance.measure('total');

measure() Return

{
    name: 'work',
    entryType: 'measure',
    startTime: 1234.567,
    duration: 456.789
}

Performance Measurement Pattern

function benchmark(fn, iterations = 1000) {
    let start = performance.now();

    for (let i = 0; i < iterations; i++) {
        fn();
    }

    let total = performance.now() - start;
    return {
        total: total,
        avg: total / iterations,
        opsPerSec: iterations / (total / 1000)
    };
}

let result = benchmark(() => {
    crypto.getRandomValues(new Uint8Array(32));
});
console.log(`${result.opsPerSec.toFixed(0)} ops/sec`);

Notes

• Uses the platform's high-resolution monotonic clock
• Resolution: nanoseconds on Linux (CLOCK_MONOTONIC), milliseconds on ESP32
• performance.now() is guaranteed to be monotonically increasing (never goes backwards)
• No PerformanceObserver API
• No performance.getEntries(), performance.getEntriesByName(), performance.clearMarks()
• No performance.memory or performance.timing (browser-only)