A sprintf Javascript implementation

Scope

This document describes the capabilities and calling conventions of quite complete sprintf implementation for Javascript. It does not explain made design decisions or inner workings of the implementation.

Capabilities

This library does provide an almost complete reimplementation of the sprintf function known from the standard c library.

The following datatypes are supported:

%%:

A literal percent sign

%b:

A binary number

%c:

An ASCII character represented by the given value

%d:

A signed decimal number

%f:

A floating point value

%o:

An octal number

%s:

A string

%x:

A hexadecimal number (lowercase characters)

%X:

A hexadecimal number (uppercase characters)

All of the usual formatting flags are supported as well. Therefore you may specify the algebraic sign, padding, alignment, width and precision. The syntax is equivalent to the one used by the sprintf c function.

Usage

The functionallity is exposed as a CommonJS module (nodejs), an AMD Module (requirejs) or as a global function, based on the environment it is used in.

It may either be used as a standalone function, or attached to the string prototype:

// Global function
var formatted = sprintf("The number is %.2f", 42);

// CommonJS
var sprintf = require("./path/to/sprintf");
var formatted = sprintf("The number is %.2f", 42);

// AMD
define("your-module", ["./path/to/sprintf"], function(sprintf) {
    var formatted = sprintf("The number is %.2f", 42);
});

The addition to the String.prototype is not done automatically to not interfere with a language primitive. You may however add a printf function to every string by calling .attach:

// Load sprintf as shown above
sprintf.attach(String.prototype);

// Now every string has a printf function available
var formatted = "%s %s".printf("foo", "bar");

License

This library is licensed under the MIT License