Description

A full implementation of the Python formatting mini-language -- built by transcoding the official Jython code with as few changes as possible.

Jython is a 20+ year-old codebase, and this module inherits much of its maturity. The code requires minimal changes to the original Jython because Java -> Javascript is a straightforward conversion. Kudos to the Jython team! https://www.jython.org/

This library is larger than alternatives, so its use case is projects that need formatting to exactly match the results of Python's str.format. Minified size is 22K.

Use

import format from 'string-format-full'

// basic: "abcdefghi"
format('abc{}ghi', 'def')

// float formatting: "3.14"
format('{:0.2f}', 3.141597)

// named args: "abcdefghijklmno42"
format('abc{arg1}ghi{arg2}mno{arg3}', {
    arg1: 'def',
    arg2: 'jkl',
    arg3: 42,
})

// array indexing: "X: 3;  Y: 5"
format('X: {0[0]};  Y: {0[1]}', [3, 5])

// nested args: "111 222"
format('{obj.first} {obj.second}', {
    'obj': {
        'first': 111,
        'second': 222,
    }
})

// array indexing + nested args:
format('{0[0].first} {0[0].second}', [
    {
        'first': 111,
        'second': 222,
    }
])

If you prefer python-style:

import format from 'string-format-full'
format.setOptions({global: true})

// "3.14"
"{:0.2f}".format(3.141597)

To allow missing values:

import format from 'string-format-full'
format.setOptions({strict: false})

// "Hello " with no error thrown for missing "World"
"{} {}".format('Hello')

See test/* files for more examples.

Browser-based <script src="...">

See browser.html.

Benefits of this Approach

1. Implements the full Python mini-language.
2. Python-style JS using the exact Python algorithms.
3. Jython has seen 20+ years of significant use and testing.
4. Unit tests in tests/.
5. No dependencies.

Drawbacks of this Approach

1. The module has a larger footprint than other, minimal modules on npmjs.org.
2. The module is likely slower than the smaller alternatives, although it probably won't matter to most projects.

Other Modules

• string-format
• python-format-js