performanceobserver observe options

• options {Object}
  • entryTypes {string[]} An array of strings identifying the types of PerformanceEntry instances the observer is interested in. If not provided an error will be thrown.
  • buffered {boolean} If true, the notification callback will be called using setImmediate() and multiple PerformanceEntry instance notifications will be buffered internally. If false, notifications will be immediate and synchronous. Default: false.

Subscribes the PerformanceObserver instance to notifications of new PerformanceEntry instances identified by options.entryTypes.

When options.buffered is false, the callback will be invoked once for every PerformanceEntry instance:

const {
  performance,
  PerformanceObserver
} = require('perf_hooks');
const obs = new PerformanceObserver((list, observer) => {
  // Called three times synchronously. `list` contains one item.
});
obs.observe({ entryTypes: ['mark'] });
for (let n = 0; n < 3; n++)
  performance.mark(`test${n}`);

const {
  performance,
  PerformanceObserver
} = require('perf_hooks');
const obs = new PerformanceObserver((list, observer) => {
  // Called once. `list` contains three items.
});
obs.observe({ entryTypes: ['mark'], buffered: true });
for (let n = 0; n < 3; n++)
  performance.mark(`test${n}`);