w3resource

JavaScript: Round a number to a specified amount of digits

JavaScript fundamental (ES6 Syntax): Exercise-152 with Solution

Write a JavaScript program to round a number to a specified amount of digits.

  • Use Math.round() and template literals to round the number to the specified number of digits.
  • Omit the second argument, decimals, to round to an integer.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const round = (n, decimals = 0) => Number(`${Math.round(`${n}e${decimals}`)}e-${decimals}`);

console.log(round(1.005, 2));
console.log(round(1.05, 2));
console.log(round(1.0005, 2));

Sample Output:

1.01
1.05
1

Pictorial Presentation:

JavaScript Fundamental: Round a number to a specified amount of digits.

Flowchart:

flowchart: Round a number to a specified amount of digits

Live Demo:

See the Pen javascript-basic-exercise-152-1 by w3resource (@w3resource) on CodePen.


Improve this sample solution and post your code through Disqus

Previous: Write a JavaScript program to run a function in a separate thread by using a Web Worker, allowing long running functions to not block the UI.
Next: Write a JavaScript program to reverse the order of the characters in the string.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.



JavaScript: Tips of the Day

Checking if a key exists in a JavaScript object?

Checking for undefined-ness is not an accurate way of testing whether a key exists. What if the key exists but the value is actually undefined?

var obj = { key: undefined };
obj["key"] !== undefined // false, but the key exists!

You should instead use the in operator:

"key" in obj // true, regardless of the actual value

If you want to check if a key doesn't exist, remember to use parenthesis:

!("key" in obj) // true if "key" doesn't exist in object
!"key" in obj   // ERROR!  Equivalent to "false in obj"

Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty:

obj.hasOwnProperty("key") // true

Checking for undefined-ness is not an accurate way of testing whether a key exists. What if the key exists but the value is actually undefined? var obj = { key: undefined }; obj["key"] !== undefined // false, but the key exists! You should instead use the in operator: "key" in obj // true, regardless of the actual value If you want to check if a key doesn't exist, remember to use parenthesis: !("key" in obj) // true if "key" doesn't exist in object !"key" in obj // ERROR! Equivalent to "false in obj" Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty: obj.hasOwnProperty("key") // true For performance comparison between the methods that are in, hasOwnProperty and key is undefined.

Ref: https://bit.ly/2CFNp1X