sprintf-js

Common errors

• TypeError: sprintf is not a function

  cause Attempting to use ES module `import` syntax in a CommonJS-only Node.js environment or without a bundler correctly transforming the import.
  fix Use CommonJS `require` syntax: `const { sprintf, vsprintf } = require('sprintf-js');` or `const sprintf = require('sprintf-js').sprintf;`

• Uncaught ReferenceError: Buffer is not defined

  cause This error typically occurs when a Node.js-specific global object (`Buffer`) is referenced in a browser environment without an adequate polyfill, often a consequence of the v1.1.1 polyfill warning.
  fix Ensure your build process includes polyfills for Node.js globals if bundling for the browser, especially when targeting environments that do not natively provide these. Verify that all required ES5/ES6+ polyfills mentioned in the `v1.1.1` warning are present.

Warnings

• gotcha As of v1.1.1, older JavaScript environments (e.g., Internet Explorer < 9) may require polyfills for certain built-in features such as `String.prototype.repeat()`, `Array.isArray()`, and `Object.create()`. Running `sprintf-js` in these environments without proper polyfills can lead to runtime errors or unexpected behavior.
  Fix: If targeting older environments, ensure necessary polyfills are included (e.g., through a bundler like Webpack/Rollup with Babel, or by explicitly importing polyfills) before `sprintf-js` is loaded.

Install

• npm install sprintf-js npm
• yarn add sprintf-js yarn
• pnpm add sprintf-js pnpm

Imports

• sprintf
  wrong:

  import { sprintf } from 'sprintf-js';

  correct:

  const { sprintf } = require('sprintf-js');

  This package is primarily a CommonJS module. While bundlers can often resolve ESM `import` statements, native Node.js environments and older browser setups require `require()` for direct usage.
• vsprintf
  wrong:

  import { vsprintf } from 'sprintf-js';

  correct:

  const { vsprintf } = require('sprintf-js');

  As a CommonJS module, `vsprintf` is exposed via `module.exports`. Using ESM `import` syntax will typically fail in non-transpiled Node.js environments.
• sprintf, vsprintf (individual require)

  var sprintf = require('sprintf-js').sprintf;
  var vsprintf = require('sprintf-js').vsprintf;

  This is the explicit usage pattern demonstrated in the package's README, clearly indicating CommonJS named exports.

Quickstart

Demonstrates basic string formatting with positional arguments, array-based formatting using `vsprintf`, numeric formatting with padding and precision, and an example of named arguments.

const { sprintf, vsprintf } = require('sprintf-js');

// Basic string formatting with argument reordering
const formattedString1 = sprintf('%2$s %3$s a %1$s', 'cracker', 'Polly', 'wants');
console.log(formattedString1); // Expected: "Polly wants a cracker"

// Formatting with an array of arguments
const alphabetLetters = ['a', 'b', 'c', 'd'];
const formattedString2 = vsprintf('The first 4 letters of the English alphabet are: %s, %s, %s and %s', alphabetLetters);
console.log(formattedString2); // Expected: "The first 4 letters of the English alphabet are: a, b, c and d"

// Example with numeric formatting (padding and precision)
const pi = 3.1415926535;
const formattedPi = sprintf('Pi to 2 decimal places: %.2f, padded to 10 chars with zero: %010.2f', pi, pi);
console.log(formattedPi); // Expected: "Pi to 2 decimal places: 3.14, padded to 10 chars with zero: 0000003.14"

// Example with named arguments (available since a minor version, not explicitly in 1.1.3 README but a common feature)
const user = { name: 'Dolly' };
const namedArgString = sprintf('Hello %(name)s', user);
console.log(namedArgString); // Expected: "Hello Dolly"