String.format for JavaScript

This is a JavaScript library for string, date and number formatting. Formatting is done using format strings almost completely compatible with the String.Format method in Microsoft .NET Framework.

How to use

To use the library, include the library itself and optionally the cultures you are targetting. Note that if no culture files are included, the invariant culture will be used.

<script src="https://cdn.jsdelivr.net/npm/@dmester/[email protected]/dist/stringformat.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/@dmester/[email protected]/dist/cultures/stringformat.en.js"></script>
<script src="https://cdn.jsdelivr.net/npm/@dmester/[email protected]/dist/cultures/stringformat.sv.js"></script>

Then you're ready to go. Here are two simple examples using indexes and object paths/named parameters.

// Index
String.format(
    "Welcome back, {0}! Last seen {1:M}", 
    "John Doe", new Date(1985, 3, 7, 12, 33)
    );
    
// Outputs: 
// Welcome back, John Doe! Last seen April 07

// Named parameters
String.format(
    "Welcome back, {user.name}! Last seen {lastseen:M}", 
    { 
        user: {
            name : "John Doe", 
            age : 42
        },
        lastseen: new Date(2009, 3, 7, 12, 33) 
    });
    
// Outputs: 
// Welcome back, John Doe! Last seen April 07

By default the browser culture will be used, given that the appropriate culture file has been referenced from the page. To set culture explicitly, use the sffjs.setCulture method, which accepts a IETF language code.

sffjs.setCulture("sv");

Browser support

sffjs is tested in IE9 and later, Chrome, Firefox and Edge, but may work in other environments.

See more

• Compatibility with .NET Framework
• More usage examples
• Working with cultures
• Extending sffjs with support for custom classes
• Reference information regarding .NET format strings