printf
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Full implementation of the `printf` family in pure JS.
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[](http://travis-ci.org/adaltas/node-printf)
A complete implementation of the **`printf` C functions family**
for [Node.JS][node], written in pure JavaScript.
**Bonus!** You get extra features, like the `%O` converter (which `inspect`s
the argument). See [Extra Features](#extra-features) below.
## Installing
Via [NPM][npm]:
``` bash
$ npm install printf
```
## Usage
Use it like you would in C (`printf`/`sprintf`):
``` javascript
var printf = require('printf');
var result = printf(format, args...);
```
It can also output the result for you, as `fprintf`:
``` javascript
var printf = require('printf');
printf(write_stream, format, args...);
```
## Features
### Flag ` ` (space)
``` javascript
assert.eql(' -42', printf('% 5d', -42));
```
### Flag `+` (plus)
``` javascript
assert.eql(' +42', printf('%+5d', 42));
```
### Flag `0` (zero)
``` javascript
assert.eql('00042', printf('%05d', 42));
```
### Flag `-` (minus)
``` javascript
assert.eql('42 ', printf('%-5d', 42));
```
### Width / precision
``` javascript
assert.eql('42.90', printf('%.2f', 42.8952));
assert.eql('042.90', printf('%06.2f', 42.8952));
```
### Numerical bases
``` javascript
assert.eql('\x7f', printf('%c', 0x7f));
assert.eql('a', printf('%c', 'a'));
assert.eql('"', printf('%c', 34));
```
### Miscellaneous
``` javascript
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('$', printf('%c', 36));
assert.eql("10", printf("%d", 10));
```
## Extra features!
### Inspector
The `%O` converter will call [`util.inspect(...)`][util_inspect] at the argument:
``` javascript
assert.eql("Debug: { hello: 'Node', repeat: false }",
printf('Debug: %O', {hello: 'Node', "repeat": false})
);
assert.eql("Test: { hello: 'Node' }",
printf('%2$s: %1$O', {"hello": 'Node'}, 'Test')
);
```
**Important:** it's a capital "O", *not* a zero!
Specifying a precision lets you control the depth up to which the object is formatted:
``` javascript
assert.eql("Debug: { depth0: { depth1_: 0, depth1: [Object] } }",
printf('Debug: %.1O', {depth0: {depth1: {depth2: {depth3: true}}, depth1_: 0}})
);
```
You can use the alternative form flag together with `%O` to disable representation of non-enumerable properties (useful for arrays):
``` javascript
assert.eql("With non-enumerable properties: [ 1, 2, 3, 4, 5, [length]: 5 ]",
printf('With non-enumerable properties: %O', [1, 2, 3, 4, 5])
);
assert.eql("Without non-enumerable properties: [ 1, 2, 3, 4, 5 ]",
printf('Without non-enumerable properties: %#O', [1, 2, 3, 4, 5])
);
```
You can use the sign flag together with `%O` to enable colors in `util.inspect`:
``` javascript
assert.eql("With colors: { bar: \u001b[33mtrue\u001b[39m, baz: \u001b[33mfalse\u001b[39m }",
printf('With colors: %+O', {bar: true, baz: false})
);
```
### Argument mapping
In addition to the old-fashioned `n$`,
you can use **hashes** and **property names**!
``` javascript
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
Length and precision can now be variable:
``` javascript
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][coffee] and are executed with [Mocha][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:
```bash
npm install
npm test
```
The test suite is run online with [Travis][travis] against the versions 6, 7, 8 and 9 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>
This package is developed by [Adaltas](http://www.adaltas.com).
[node]: http://nodejs.org "The Node.JS platform"
[npm]: https://github.com/isaacs/npm "The Node Package Manager"
[util_inspect]: http://nodejs.org/api/util.html#util_util_inspect_object_showhidden_depth_colors "util.inspect() documentation"
[travis]: https://travis-ci.org "Continuous Integration system"
[mocha]: http://mochajs.org/ "The Mocha test framework"
[coffee]: http://coffeescript.org/