Yet another format string function

Fast, small and basic string templating function. This library is intended for use cases where the position of parameters in a format string is not known at compile-time.

For situations with predictable/constant string formats, using JavaScript's built-in string templating is highly recommended.

Getting Started

1. Add the library into your project.

   npm install @superior-one/format_string

2. Import default function and start using.
   • Named parameters:

     import format_string from "@superior-one/format_string";
        
     const format_tag = "({userTag}){name}, [{hash}]";
     const format_email = "<{email}>{name}, {hash}";
     const args = {
       email: "[email protected]",
       name: "John Doe",
       hash: "18c54d073b2",
       userTag: "@john" 
     };
        
     const text0 = format_string(format_tag, args);
     console.log(text0); // (@john)John Doe, [18c54d073b2]
        
     const text1 = format_string(format_email, args);
     console.log(text1); // <[email protected]>John Doe, 18c54d073b2

   • Positional parameters:

     import format_string from "@superior-one/format_string";
        
     const format = "{2} {1} {0} {0} {2}\n{2} {0} {1} {0} {2}\n{2} {0} {0} {1} {2}\n";
     const text = format_string(format, ["a", 5, "|"]);
        
     console.log(text);
     // | 5 a a |
     // | a 5 a |
     // | a a 5 |

Format Syntax

Consider arg="value"

| Format | Output | Description | |-----------------|-----------------|---------------------------------------------------------------------------| | {arg} | value | Replaces {arg} with the value of arg | | {arg } | {arg } | Treats {arg } as a string as it doesn't follow correct formatting | | { arg} | { arg} | Treats { arg} as a string since it doesn't follow correct formatting | | {arg arg} | {arg arg} | Treats {arg arg} as a string since it doesn't follow correct formatting | | {\narg} | {\narg} | Treats {\narg} as a string since it doesn't follow correct formatting | | {} | {} | Empty placeholders are ignored and treats as a string | | {{arg}} | {arg} | Escapes the placeholder syntax | | {{{{arg}}}} | {{{arg}}} | Escapes the inner placeholder syntax, outputting {{{arg}}} as a string | | {{{ {arg} }}} | {{{ value }}} | Inserts value within triple curly braces, outputting {{{ value }}} |

Avoid using space, feed, tab and separator characters in placeholder names as they will be interpreted as strings, not placeholders.

List of invalid placeholder characters;

• {
• }
• ' '
• \f
• \n
• \r
• \t
• \v
• \u00a0
• \u1680
• \u2000 to \u200a
• \u2028
• \u2029
• \u202f
• \u205f
• \u3000
• \ufeff

Building the Project

Build step only generates type decleration and CommonJS version.

npm install
npm run build

Contributing

Pull requests are welcome, especially ideas for time and memory allocation reduction.

Benchmarks

Tested against some popular packages with four parameters and single escape.

Keep in mind some of the listed libraries provides more features like number formatting, padding etc.

Test Environment:
CPU       : AMD Ryzen 9 5950X 16-Core @ 32x 5.177GHz
OS        : x86_64 Linux 6.6.3-1
node      : v20.7.0
vitest    : v1.0.4
tinybench : v2.5.1

  name                                                        hz     min     max    mean     p75     p99    p995    p999     rme  samples
· @superior-one/format_string with positional args  2,693,972.54  0.0003  0.9917  0.0004  0.0004  0.0004  0.0006  0.0016  ±0.31%  2693973
· @superior-one/format_string with named args       2,260,906.19  0.0004  0.5987  0.0004  0.0004  0.0009  0.0009  0.0010  ±0.20%  2260907  
· string-template with named args                     858,246.92  0.0011  0.2475  0.0012  0.0011  0.0021  0.0022  0.0024  ±0.16%   858247  
· string-template with positional args              1,016,520.83  0.0009  0.1932  0.0010  0.0010  0.0011  0.0012  0.0019  ±0.11%  1016521  
· @stdlib/string-format with positional args        1,771,259.33  0.0005  0.2183  0.0006  0.0006  0.0007  0.0008  0.0011  ±0.19%  1771260  
· string-format with positional args                  548,726.51  0.0017  0.2494  0.0018  0.0018  0.0021  0.0029  0.0036  ±0.22%   548727  
· string-format with named args                       377,298.69  0.0025  0.1892  0.0027  0.0026  0.0029  0.0030  0.0061  ±0.16%   377299 
· pupa with positional args                           522,948.55  0.0018  0.1503  0.0019  0.0019  0.0021  0.0035  0.0041  ±0.15%   522949  
· pupa with named args                                455,937.12  0.0021  0.9894  0.0022  0.0022  0.0038  0.0043  0.0051  ±0.23%   455938  
· string replaceAll positional args                 1,619,706.37  0.0006  0.1692  0.0006  0.0006  0.0007  0.0008  0.0011  ±0.13%  1619707  
· string replaceAll named args                      1,705,262.53  0.0005  0.2296  0.0006  0.0006  0.0007  0.0011  0.0012  ±0.07%  1705263  

BENCH  Summary

@superior-one/format_string with positional args - index.bench.js > 
 1.19x faster than @superior-one/format_string with named args
 1.52x faster than @stdlib/string-format with positional args
 1.58x faster than string replaceAll named args
 1.66x faster than string replaceAll positional args
 2.65x faster than string-template with positional args
 3.14x faster than string-template with named args
 4.91x faster than string-format with positional args
 5.15x faster than pupa with positional args
 5.91x faster than pupa with named args
 7.14x faster than string-format with named args

License

This project is licensed under the terms of the MIT license.