JSPM – printf@0.3.0

Package Exports

printf

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (printf) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

A complete implementation of the printf C functions family for Node.JS, written in pure JavaScript.

Bonus! You get extra features, like the %O converter (which inspects the argument). See Extra Features below.

Installing

Via NPM:

$ npm install printf

Usage

Use it like you would in C (printf/sprintf):

var printf = require('printf');
var result = printf(format, args...);

It can also output the result for you, as fprintf:

var printf = require('printf');
printf(write_stream, format, args...);

Features

Flag (space)

assert.eql('  -42', printf('% 5d', -42));

Flag `+` (plus)

assert.eql('  +42', printf('%+5d', 42));

Flag `0` (zero)

assert.eql('00042', printf('%05d', 42));

Flag `-` (minus)

assert.eql('42   ', printf('%-5d', 42));

Width / precision

assert.eql('42.90', printf('%.2f', 42.8952));
assert.eql('042.90', printf('%06.2f', 42.8952));

Numerical bases

assert.eql('\x7f', printf('%c', 0x7f));
assert.eql('a', printf('%c', 'a'));
assert.eql('"', printf('%c', 34));

Miscellaneous

assert.eql('10%', printf('%d%%', 10));
assert.eql('+hello+', printf('+%s+', 'hello'));
assert.eql("a", printf("%c", "a"));
assert.eql('"', printf("%c", 34));
assert.eql('$', printf('%c', 36));
assert.eql("10", printf("%d", 10));

Extra features!

Inspector

The %O converter will call util.inspect(...) at the argument:

assert.eql("Debug: { hello: 'Node', repeat: false }",
  printf('Debug: %O', {hello: 'Node', "repeat": false})
);
assert.eql("Test: { hello: 'Node' }",
  printf('%2$s: %1$O', {"hello": 'Node'}, 'Test')
);

Important: it's a capital "O", not a zero!

Specifying a precision lets you control the depth up to which the object is formatted:

assert.eql("Debug: { depth0: { depth1_: 0, depth1: [Object] } }",
  printf('Debug: %.1O', {depth0: {depth1: {depth2: {depth3: true}}, depth1_: 0}})
);

You can use the alternative form flag together with %O to disable representation of non-enumerable properties (useful for arrays):

assert.eql("With non-enumerable properties: [ 1, 2, 3, 4, 5, [length]: 5 ]",
  printf('With non-enumerable properties: %O', [1, 2, 3, 4, 5])
);
assert.eql("Without non-enumerable properties: [ 1, 2, 3, 4, 5 ]",
  printf('Without non-enumerable properties: %#O', [1, 2, 3, 4, 5])
);

Argument mapping

In addition to the old-fashioned n$, you can use hashes and property names!

assert.eql('Hot Pockets',
  printf('%(temperature)s %(crevace)ss', {
    temperature: 'Hot',
    crevace: 'Pocket'
  })
);
assert.eql('Hot Pockets',
  printf('%2$s %1$ss', 'Pocket', 'Hot')
);

Positionals

Lenght and precision can now be variable:

assert.eql(' foo', printf('%*s', 'foo', 4));
assert.eql('      3.14', printf('%*.*f', 3.14159265, 10, 2));
assert.eql('000003.142', printf('%0*.*f', 3.14159265, 10, 3));
assert.eql('3.1416    ', printf('%-*.*f', 3.14159265, 10, 4));

Development

Tests are written in CoffeeScript executed with Mocha. To use it, simple run npm install, it will install Mocha and its dependencies in your project's node_modules directory followed by npm test.

To run the tests:

npm install
npm test

The test suite is run online with Travis against the versions 0.9, 0.10 and 0.11 of Node.js.

Contributors

David Worms https://github.com/wdavidw
Aluísio Augusto Silva Gonçalves https://github.com/AluisioASG
Xavier Mendez https://github.com/jmendeth
LLeo https://github.com/lleo
Derrell Lipman https://github.com/derrell

printf