util.format() Method in Node.js

Introduction

The util.format() method in Node.js is a utility function used to format strings using placeholders. It works similarly to printf() in C, allowing developers to insert values dynamically into a string.

Syntax

util.format(format[, ...args])

This function takes a format string as its first argument, followed by values to replace placeholders in that string.

Parameters

• format: A string that can contain placeholders like %s, %d, and %j.
• ...args: Values to replace the placeholders in the format string.

Common Placeholders

• %s: Replaces with a string.
• %d: Replaces with a number.
• %j: Replaces with a JSON representation.
• %%: Outputs a literal percent sign (%).

Return Value

Returns a formatted string with all placeholders replaced by the corresponding argument values.

Example

const util = require('util');

const message = util.format('Name: %s, Age: %d, Details: %j', 'John', 28, { city: 'Delhi' });

console.log(message);
  

Output

Name: John, Age: 28, Details: {"city":"Delhi"}

Use Case

The util.format() method is ideal for dynamically constructing output strings in logs, debugging messages, or anywhere you need formatted output. It's especially helpful in server-side applications to display clear and readable data.

Conclusion

With util.format(), Node.js developers can create neatly formatted strings using simple syntax. It’s a handy tool that brings clarity and efficiency to string construction in backend applications.