printf-ts

pure typescript implementation of printf-family with type checking

Usage

import { printf } from 'printf-ts';

// Hello printf 1 1.20
printf("Hello %s %d %.2lf", "printf", 1, 1.2)

Features

1. vsprintf(format, args: [...]): string

2. sprintf(format, ...args: [...]): string

3. vprintf(format, args: [...]): number

4. printf(format, ...args: [...]): number

5. vprintfln(format, args: [...]): number

6. printfln(format, ...args: [...]): number

• 1 ~ 2 Returns the result as a string
• 3 ~ 4 Writes the results to the stdout, returns the number of characters printed
• 5 ~ 6 Writes the results to the stdout, returns the number of characters printed. if nodejs, append \n to the end(not affect to return value)

Supported format specifiers

see cppreference-printf for each description of specifier

• flags: +, -, , #, 0
• width, precision
  • support wildcard(*)
• length modifier: h, hh, l, ll, L, j, z, t
• conversion specifier: %c, %s, %d, %i, %u, %o, %x, %X, %f, %F, %e, %E, %g, %G, %p, %%

types

• if argument is negative and format specifier is unsigned, it will not convert to unsigned type
• argument is not converted to a number of specific bits
• if origin type was unsigned, find it in signed type

specifier	argument type	description
%c	string	str[0] ?? ''
%c	number	utf8 code point
%s	string
%n	null	please use sprintf(...).length

integer

%d, %i, %u, %o, %x, %X

• short|int -> number
• long|long long|intmax_t|ssize_t|ptrdiff_t -> bigint

Floating point

%f, %F, %e, %E, %g, %G

• double|long double -> number
  • if value in [infinity, -infinity, NaN]
    • if specifier is uppercase(F,E,G,A) => "INF", "-INF", "NAN"
    • else => "inf", "-inf", "nan"
• NaN always treated as a positive value

Pointer

%p

• void* -> bigint
  • if value is 0n => "(nil)"
  • else => "0x" + value.toString(16)

Wildcard

*

• int -> number