@cesium/engine/Source/Core/getTimestamp.js

CesiumJS is a JavaScript library for creating 3D globes and 2D maps in a web browser without a plugin.

/**
 * Gets a timestamp that can be used in measuring the time between events.  Timestamps
 * are expressed in milliseconds, but it is not specified what the milliseconds are
 * measured from.  This function uses performance.now() if it is available, or Date.now()
 * otherwise.
 *
 * @function getTimestamp
 *
 * @returns {number} The timestamp in milliseconds since some unspecified reference time.
 */
let getTimestamp;

if (
  typeof performance !== "undefined" &&
  typeof performance.now === "function" &&
  isFinite(performance.now())
) {
  getTimestamp = function () {
    return performance.now();
  };
} else {
  getTimestamp = function () {
    return Date.now();
  };
}
export default getTimestamp;