prototypes

prototypes

Some common prototypes for node.js: string.startsWith(), object.countProperties() and more. Functions are added using Object.defineProperty() to avoid polluting new objects.

Installation

Simply install using npm:

npm install prototypes

Or add to the dependencies of your project in your package.json.

Usage

This package adds some useful prototypes to String. To use in your package, you just have to require prototypes:

require('prototypes');

You do not need to assign the result to any variable, and in fact JSHint (and similar code checkers) may complain about an unused variable if you do this:

var prototypes = require('prototypes');

This last form is only required if you use any of the exported functions, which should be seldom the case.

String Prototypes

The following string prototypes are provided.

string.startsWith(str)

Check that the current string starts with the given substring. Example:

'pepitus'.startsWith('pep');
  \=> true

string.endsWith(str)

Check that the current string ends with the given substring. Example:

'pepitus'.startsWith('tus');
  \=> true

string.substringUpTo(str)

Return the piece of string until the argument is found. Example:

'hi.there'.substringUpTo('.');
   \=> 'hi'

string.substringUpToLast(str)

Return the piece of string until the last occurrence of the argument. Example:

'hi.there.you'.substringUpToLast('.');
   \=> 'hi.there'

string.substringFrom(str)

Return the piece of string starting with the argument; empty string if not found. Example:

'hi.there'.substringFrom('.');
   \=> 'there'

string.substringFromLast(str)

Return the piece from the last occurrence of the argument; empty string if not found. Example:

'hi.there.you'.substringFromLast('.');
   \=> 'you'

string.contains(str)

Find out if the string contains the argument at any position. Example:

'abcde'.contains('bcd');
   \=> true

string.replaceAll(str, replacement)

Replace all occurrences of a string with the replacement. Example:

'pepitus'.replaceAll('p', 'c');
   \=> 'cecitus'

string.repeat(number)

Repeat the given string a few times. Example:

'ab'.repeat(3);
   \=> 'ababab'

string.capitalize()

Capitalize a string: first letter upper case, rest as is. Example:

'hello'.capitalize();
   \=> 'Hello'

Object Functions

For objects some care must be taken before overwriting Object.prototype: otherwise it might break all code that does not check for hasOwnProperty(). See MDN help. In this library all extensions are done using Object.defineProperty() which does not pollute objects as the new properties are not enumerable. Again, see MDN help.

object.countProperties(filter)

Count the number of properties in an object. Does not count inherited properties: uses Object.keys(). Example:

{a: 'a'}.countProperties();
  \=> 1

You can also pass a string or a function as a filter:

{hello: 'a'}.countProperties('ll');
  \=> 1

{hello: 'a'}.countProperties(function(key) { return key.length == 5 });
  \=> 1

object.overwriteWith(overwriter)

Overwrite properties in the original with the given object. Example:

{a: 'a'}.overwriteWith({b: 'b'});
  \=> {a: 'a', b: 'b'}

Math-related Functions

There are math functions in Math, in Number.prototype and even as globals, e.g. parseInt().

parseInt(string)

By default parseInt() requires a radix (or base), or it will recreate the radix itself: if the string starts with a leading zero, then it interprets that you are parsing an octal number.

// unsafe parseInt()
parseInt('010');
  \=> 8

This library replaces the global function with a safe version that uses radix 10 unless told otherwise. The last person that wanted to convert octal with leading zeroes is probably programming in Lisp anyway. Example:

parseInt('010');
  \=> 10

Math.log10(number)

Logarithm in base 10. Example:

Math.log10(10);
  \=> 1

number.toRad()

Convert a number in degrees to radians. Example:

var n = 180;
n.toRad();
  \=> 3.141592653589793