Sprintf

JS implementation of the useful sprintf c-function.
We try to keep the API as close to the original implementation as possible, while some features might be hard to implement in JavaScript the following features are available:

Placeholder support.

%i: Integer (decimal)
%d: Integer (decimal)
%o: Octal
%x: Hex (lower case)
%X: Hex (upper case)
%e: Scientific notation (lower case)
%E: Scientific notation (upper case)
%f: Float
%a: Hex float (lower case)
%A: Hex float (upper case)
%c: Char
%s: String
%j: Json (object which will be stringified if possible)

Precision support for float.

By using the %.<number>f syntax, you are able to specify precision for float types (f, a, A). If precision is higher than the value passed, 0's will be appended to the result and it will not be rounded, while if the value is longer (char count) than the precision value, it will cut the result at the specific point.

Example:

const floatP  = sprintf('abc %.5f', 1.12345678); // 'abc 1.12345'
const floatP2 = sprintf('abc %.5f', 1.12);       // 'abc 1.12000'

Left-padding support for integer.

The same syntax as for floats can be used to pad integers (d, i) with 0's.
If the pad value is lower than the length of the integer, nothing will happen.

const intP  = sprintf('abc %.5s', 123); // 'abc 00123'
const intP2 = sprintf('abc %.1s', 123); // 'abc 123'

Sub-strings

The same syntax as for integer and floats can be used to substring strings.
If the string is shorter than the value, nothing will be changed.

const stringP  = sprintf('abc %.5s', 'abc123abc');     // 'abc abc12'
const stringP2 = sprintf('abc %.10000s', 'abc123abc'); // 'abc abc123abc'

Missing features to be implemented in future versions:

• Flags
  • %.* precision specifier
  • width specifier
  • *width specifier
  • %- left justify
  • %+ right justify
  • %space pad,
  • %# prefix for octal and hex
  • %0 0-pad
• Specifiers
  • g, G for shortest rep of %e/%f & %E/%F.