IntervalTimer.js

/**
 * @author Nandan V
 * Sunday, 26 July 2020 8:33 AM
 * @description Singleton class that handles the <b>timing of tests</b> and
 * specs. <br/> The class is singleton as <u>javascript does not support
 * multiple timer instances<u/>.
 */
class IntervalTimer {
 /**
 * @description Constructor for Timer.
 * @param interval Sets the interval for running the timer.
 * @param callBack The callback function to be executed.
 * @return {IntervalTimer} If exists, the existing object.
 */
 constructor(interval = 10, callBack = () => {}) {
 this.prevInterval = 0
 if (this.instance == null) {
 this.interval = interval
 this.callBack = callBack
 this.instance = this
 } else {
 return this.instance
 }
 }

 /**
 * @description Starts the timer.
 */
 startTimer() {
 this.timer = setInterval(this.callBack, this.interval)
 }

 /**
 * @description Resets the timer.
 * @return {number} Elapsed time in milliseconds.
 */
 resetTimer() {
 clearInterval(this.timer)
 this.callBack = () => {}
 return this.getElapsedTime()
 }

 /**
 * @return {number} Elapsed time in milliseconds since reset.
 */
 getElapsedTime(offset = 0) {
 this.timeElapsed = this.timer - this.prevInterval
 this.prevInterval = this.timer
 return this.timeElapsed - offset
 }

 /**
 * @return {number} Elapsed time since start.
 */
 getRunTime() {
 return this.timer
 }
}

/**
 * @author Nandan V
 * Saturday, 01 August 2020 8:33 AM
 * @description Example usage
 */
const ExampleIntervalTimer = function (output = (v) => console.log(v)) {
 /**
 * Create am object with default settings.
 * @type {IntervalTimer} Used to get timing information.
 */
 const timer = new IntervalTimer()
 timer.startTimer()

 // ... Initialization code ...
 // I generally use it for timing tests in Jasmine JS.

 /**
 * Gets the runtime till this point.
 * Can be subtracted from ElapsedTime to offset timing of initialization code.
 */
 const initOffset = timer.getRunTime()

 // ... A test ...
 // The time taken to run the test.
 output(timer.getElapsedTime(initOffset))

 /**
 * Returns the elapsed time and resets the timer to 0.
 */
 output(timer.resetTimer())
}

export { IntervalTimer, ExampleIntervalTimer }