fmt-subs !npm version !npm license

Helps with complex printf-style formatting.

What is printf-style formatting.

Shortly: printf format string on wiki.

!printf demo

In JavaScript world this format is used at:

- Native Browser & Node.js console's .log(), .info() etc (about string substitutions on MDN)
- Incredibly popular debug utility
- printf package
- ...and many-many others

The problem and the solution

The problem appears when you have to deal with a huge format strings with a lot of substitutions and you have to keep in mind relations between them and actual values, passed next after format string. Or, for example, when you need dynamic construction of format string.

This package solves it with a bit of abstractions:

``ts
import { fmt, sub } from 'fmt-subs'

function part1() {
return fmtPart 1: ${sub({ foo: true }, '%o')}
}

function part2() {
return fmtPart 2: ${sub([1, 2, 3], '%s')}
}

console.log(...fmt${part1()} ${part2()}.assemble())
// Part 1: { foo: true } Part 2: [ 1, 2, 3 ]

console.log(...fmt${part2()} ${part1()}.assemble())
//Part 2: [ 1, 2, 3 ] Part 1: { foo: true }
`

Installation

Use your favorite package manager:

`shell
npm i fmt-subs
yarn add fmt-subs
pnpm add fmt-subs
`

Usage

1. Construct fmt (nest fmts to each other, insert substitutions, concatenate them)
2. Assemble it .assemble() to a final array of arguments and pass it to your formatting function (console.log, debug etc)

`ts
import { fmt, sub, Fmt } from 'fmt-subs'

// construction
fmtHello!
fmtHenno? ${fmtNested fmt}

// insert substitutions
fmtA: ${fmt.sub(1_002, '%d')}
fmtB: ${sub(false, '{{ bool }}')}

// concat
fmt1: .concat(fmt2: , fmt3: )
Fmt.concat(fmt1, fmt 2)

// assemble
fmtHey, ${sub(5, '%d')}.assemble() == ['Hey, %d', 5]
``

API

See here.