JavaScript Date.now()
Syntax & Examples

Date.now() static-method

The Date.now() method returns the number of milliseconds elapsed since January 1, 1970 00:00:00 UTC, ignoring leap seconds. It provides a quick and efficient way to get the current timestamp in milliseconds.

Syntax of Date.now()

The syntax of Date.now() static-method is:

Date.now()

This now() static-method of Date returns the numeric value corresponding to the current time—the number of milliseconds elapsed since January 1, 1970 00:00:00 UTC, with leap seconds ignored.

Return Type

Date.now() returns value of type Number.


✐ Examples

1 Using Date.now() to get the current timestamp

In JavaScript, we can use the Date.now() method to get the current timestamp in milliseconds.

For example,

  1. We call the Date.now() method to get the current timestamp.
  2. The current timestamp is stored in the variable currentTimestamp.
  3. We log currentTimestamp to the console using console.log() method.

JavaScript Program

const currentTimestamp = Date.now();
console.log(currentTimestamp);

Output

1625151243567

2 Calculating the difference between two timestamps

In JavaScript, we can use the Date.now() method to calculate the difference between two timestamps.

For example,

  1. We get the current timestamp using Date.now() and store it in the variable start.
  2. We simulate a delay using setTimeout() method with a delay of 1 second (1000 milliseconds).
  3. After the delay, we get another timestamp using Date.now() and store it in the variable end.
  4. We calculate the difference between end and start and store it in the variable duration.
  5. We log duration to the console using console.log() method.

JavaScript Program

const start = Date.now();
setTimeout(() => {
  const end = Date.now();
  const duration = end - start;
  console.log(`Elapsed time: ${duration} ms`);
}, 1000);

Output

Elapsed time: 1000 ms

3 Using Date.now() to measure execution time of a function

In JavaScript, we can use the Date.now() method to measure the execution time of a function.

For example,

  1. We define a function exampleFunction that performs some operations.
  2. We get the timestamp before the function execution using Date.now() and store it in the variable start.
  3. We call the exampleFunction.
  4. We get the timestamp after the function execution using Date.now() and store it in the variable end.
  5. We calculate the execution time by subtracting start from end and store it in the variable executionTime.
  6. We log executionTime to the console using console.log() method.

JavaScript Program

function exampleFunction() {
  for (let i = 0; i < 1000000; i++); // Simulate some work
}
const start = Date.now();
exampleFunction();
const end = Date.now();
const executionTime = end - start;
console.log(`Execution time: ${executionTime} ms`);

Output

Execution time: 15 ms

Summary

In this JavaScript tutorial, we learned about now() static-method of Date: the syntax and few working examples with output and detailed explanation for each example.