Nono.MA

Measure Time Elapsed with TypeScript

You can measure the time elapsed during the execution of TypeScript commands by keeping a reference to the start time and then subtracting the current time at any point on your program from that start time to obtain the time elapsed between two points in time.

const start = new Date().getTime();

// Run some code..

let elapsed = new Date().getTime() - start;

Let's create two helper functions to get the current time (i.e. now) and the elapsed time at any point from that moment.

// Returns current time
// (and, if provided, prints the event's name)
const now = (eventName = null) => {
    if (eventName) {
      console.log(`Started ${eventName}..`);
    }
    return new Date().getTime();
}

// Store current time as `start`
let start = now();

// Returns time elapsed since `beginning`
// (and, optionally, prints the duration in seconds)
const elapsed = (beginning = start, log = false) => {
    const duration = new Date().getTime() - beginning;
    if (log) {
        console.log(`${duration/1000}s`);
    }
    return duration;
}

With those utility functions defined, we can measure the duration of different events.

// A promise that takes X ms to resolve
function sleep(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
}

// Measure duration (while waiting for 2 seconds)
(async function demo() {
    const waitInSeconds = 2;
    let beginning = now(`${waitInSeconds}-second wait`);
    // Prints Started 2-second wait..
    await sleep(waitInSeconds * 1000);
    elapsed(beginning, true);
    // Prints 2.004s
})();

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