» Javascript equivalent for PHP's function_exists

PHP to Javascript Project: php.js

php.jsThis article is part of the 'Porting PHP to Javascript' Project, which aims to decrease the gap between developing for PHP & Javascript.

A lot of people are familiar with PHP's functions, and though Javascript functions are often quite similar, some functions may be missing or addressed differently. The Javascript implementations should be as compliant with the PHP versions as possible, a good indication is that the PHP function manual could also apply to the Javascript version.

Porting crucial PHP functions to Javascript can be fun & useful. Currently some PHP functions have been added, but readers are encouraged to contribute and improve functions by adding comments. Eventually the goal is to save all the functions in one php.js file and make it publicly available for your coding pleasure.

If you choose to contribute, let me know how you want to be credited in the function's comments. You may also want to subscribe to RSS so you receive updates whenever new functions are posted.

This is a Javascript version of the PHP function: function_exists.

PHP function_exists

Description

function_exists - Return TRUE if the given function has been defined

bool function_exists( string function_name )

Checks the list of defined functions, both built-in (internal) and user-defined, for function_name.

Parameters

  • function_name

    The function name, as a string.

Return Values

Returns TRUE if function_name exists and is a function, FALSE otherwise.

Note: This function will return FALSE for constructs, such as include_once() and echo().

Javascript function_exists

Source

This is the main source of the Javascript version of PHP's function_exists

function function_exists( function_name ) {
    // http://kevin.vanzonneveld.net
    // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   improved by: Steve Clay
    // +   improved by: Legaev Andrey
    // *     example 1: function_exists('isFinite');
    // *     returns 1: true
 
 
    if (typeof function_name == 'string'){
        return (typeof window[function_name] == 'function');
    } else{
        return (function_name instanceof Function);
    }
}

Examples

Currently there is 1 example

Example 1

This is how you could call function_exists()
function_exists('isFinite');
And that would return
true

More about this Project

Download php.js

To easily include it in your code, every function currently available is stored in

Normal

Namespaced What is 'namespaced?'

To download use Right click, Save Link As
Generally the best way is to use a minified version and gzip it



Testing the functions

The number of functions is growing fast and so it becomes hard to maintain quality.

To defeat that danger of bad code, syntax errors, etc, I've added a new feature: php.js tester.

It is an automatically generated page that includes ALL functions in your browser, and then extracts specific testing information from each function's comments. This info is then used to run the function, and the return value is compared to a predefined one.

This way code is always checked on syntax errors, and if it doesn't function correctly anymore after an update, we should also be able to detect it more easily.

If you want, go check it out.


Credits

Respect & awards go to everybody who has contributed in some way so far:

medalmedalMichael White (link) for contributing to:
 array_count_values, get_included_files, include, include_once, require, require_once, md5, number_format, parse_str, printf, sha1, sprintf, str_pad, strnatcmp, http_build_query, floatval, is_object, print_r
spacemedal_argos for contributing to:
 array_fill, array_pad, array_product, array_rand, compact, count, range, abs, defined, ip2long, long2ip, implode, strcmp, ucwords
spacemedalJonas Raoni Soares Silva (link) for contributing to:
 shuffle, abs, setcookie, number_format, number_format, soundex, str_repeat, str_replace, str_rot13, ucwords, wordwrap, wordwrap
spacemedalLegaev Andrey for contributing to:
 end, reset, file, file_get_contents, function_exists, include, include_once, http_build_query, is_array, is_object
spacemedalAtes Goral (link) for contributing to:
 array_change_key_case, array_count_values, array_diff_key, get_class, preg_quote, addslashes, count_chars, str_rot13, stripslashes
spacemedalPhilip Peterson for contributing to:
 sizeof, round, echo, nl2br, str_replace, strchr, urldecode, urlencode, var_export
spacemedalMartijn Wieringa for contributing to:
 str_ireplace, str_split, strcasecmp, stripos, strnatcmp, substr
spacemedalWebtoolkit.info (link) for contributing to:
 crc32, md5, sha1, utf8_decode, utf8_encode
 
spacemedalCarlos R. L. Rodrigues (link) for contributing to:
 array_chunk, array_unique, date, levenshtein
spacemedalAsh Searle (link) for contributing to:
 basename, printf, sprintf
spacemedalErkekjetter for contributing to:
 ltrim, rtrim, trim
spacemedalmarrtins for contributing to:
 array_change_key_case, addslashes, stripslashes
spacemedalAlfonso Jimenez (link) for contributing to:
 array_reduce, strpbrk
spacemedalAman Gupta for contributing to:
 base64_decode, utf8_decode
spacemedalArpad Ray (mailto:arpad@php.net) for contributing to:
 serialize, unserialize
spacemedalKarol Kowalski for contributing to:
 array_reverse, abs
spacemedalThunder.m for contributing to:
 base64_decode, base64_encode
spacemedalTyler Akins (link) for contributing to:
 base64_decode, base64_encode
spacemedalmdsjack (link) for contributing to:
 include, trim
spacemedalAlexander Ermolaev (link) for contributing to:
 trim
spacemedalAllan Jensen (link) for contributing to:
 number_format
spacemedalAndrea Giammarchi (link) for contributing to:
 array_map
spacemedalBayron Guevara for contributing to:
 base64_encode
spacemedalBenjamin Lupton for contributing to:
 number_format
spacemedalBrad Touesnard for contributing to:
 date
spacemedalBrett Zamir for contributing to:
 str_split
spacemedalCagri Ekin for contributing to:
 parse_str
spacemedalCord for contributing to:
 is_array
spacemedalDavid for contributing to:
 is_numeric
spacemedalDavid James for contributing to:
 get_class
spacemedalDxGx for contributing to:
 trim
spacemedalFGFEmperor for contributing to:
 mktime
spacemedalFelix Geisendoerfer (link) for contributing to:
 array_key_exists
spacemedalFremyCompany for contributing to:
 isset
spacemedalGabriel Paderni for contributing to:
 str_replace
spacemedalLeslie Hoare for contributing to:
 rand
spacemedalLincoln Ramsay for contributing to:
 basename
spacemedalMeEtc (link) for contributing to:
 date
spacemedalMick@el for contributing to:
 stripslashes
spacemedalNick Callen for contributing to:
 wordwrap
spacemedalOzh for contributing to:
 dirname
spacemedalPedro Tainha (link) for contributing to:
 unserialize
spacemedalPeter-Paul Koch (link) for contributing to:
 date
spacemedalPhilippe Baumann for contributing to:
 empty
spacemedalSakimori for contributing to:
 strlen
spacemedalSanjoy Roy for contributing to:
 array_diff
spacemedalSimon Willison (link) for contributing to:
 str_replace
spacemedalSteve Clay for contributing to:
 function_exists
spacemedalSteve Hilder for contributing to:
 strcmp
spacemedalSteven Levithan (link) for contributing to:
 trim
spacemedalT0bsn for contributing to:
 crc32
spacemedalThiago Mata (link) for contributing to:
 call_user_func_array
spacemedalTim Wiel for contributing to:
 date
spacemedalXoraX (link) for contributing to:
 dirname
spacemedalbaris ozdil for contributing to:
 mktime
spacemedalbooeyOH for contributing to:
 preg_quote
spacemedaldjmix for contributing to:
 basename
spacemedalduncan for contributing to:
 array_unique
spacemedalecho is bad for contributing to:
 echo
spacemedalgabriel paderni for contributing to:
 mktime
spacemedalger for contributing to:
 html_entity_decode
spacemedaljohn (link) for contributing to:
 html_entity_decode
spacemedalkenneth for contributing to:
 explode
spacemedalpenutbutterjelly for contributing to:
 str_ireplace
spacemedalstensi for contributing to:
 intval

Your name here?

Contributing is as easy as adding a comment with better code, or code for a new function.
Any contribution leading to improvement will directly get your name & link here.


Coming Project features

Project features that we are currently working on:

  • Versioning. Individual functions are versioned, but the entire library should be versioned as well.
  • Light. A lightweight version of php.js should be made available with only common functions in it.

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tags: programming, php, javascript
category: Programming - Javascript - PHP equivalents
read: 1,496 times

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Comments

#10. Kevin on 15 January 2008

Kevin@ Andrea Giammarchi: Wow you did some impressive work that I was unaware of. Cool :) I will look into the define function later today and add it here, thanks a lot for that.

About the PHP vs JS stuff.. I'm not trying to port or emulate the entire language or control structures of PHP. Indeed I don't see the need because (and this is quite a statement), Javascript seems to have more elegant features in that category anyway.

However in my eyes, PHP does provide a large set of standard functions that make developing very easy, and some of them don't have good standard Javascript implementations, though they often would be great to have client-side.
... [more]
So in this project by also providing the functions separately, I hope to keep people from inventing the wheel and give them a head start.

Thanks for your comment Andrea, well appreciated. And respect for your Overbyte editor & JHP environment. The idea is very interesting, and I can see it's all coded with very high skill.

#9. Andrea Giammarchi on 14 January 2008

Andrea GiammarchiIf you are interested in some similar stuff, looks for JHP setting in overbyte editor.

Finally, You could use my define function too, that accept only scalar values as PHP and is compatible with IE, FireFox, Safari and Opera (Opera devs will fix soon their const keyword ... I guess ...)

http://webreflection.blogspot.com/2007/10/cow-javascript-define-php-like-function.html
... [more]
However, nice stuff .. not so useful in my mind because of different languages nature (I would like to have JS behaviours in PHP, for example :D) but good luck for the project

#8. Legaev Andrey on 08 January 2008

Legaev Andrey@ Kevin: I'm sorry. Not necessary to enlist my email. I did not think about spammers :)

#7. Kevin on 07 January 2008

Kevin@ Legaev Andrey: Hi, I've updated the function and changed your name. I wasn't sure you really want me to enlist your email address?

#6. Legaev Andrey (aka Andrey) on 07 January 2008

Legaev Andrey (aka Andrey)Sorry for my short previous comment and my bad English. Below full version.

If we pass function_name as String then all ok. But if we pass the link to function (link to Object-function) then
this function returns false. In my opinion in this case this function should return true when first
parameter is instance of Function.
... [more]
function function_exists_new( function_name ) {
if (typeof function_name == \'string\')
return (typeof window[function_name] == \'function\');
else
return (function_name instanceof Function);
}

P.S. Please, change my name to Legaev Andrey <legaev_andrey@mail.ru>. Thanks.

#5. Kevin on 06 January 2008

Kevin@ Cord: Thanks for noticing. Fixed!

#4. Cord on 06 January 2008

Cord>>function is_array() {
should be
>>function is_array(a) {

#3. Kevin on 04 January 2008

Kevin@ Steve Clay & Andrey: Thanks You guys I've updated the function. I left the old code in the comments for future reference.

#2. Andrey on 04 January 2008

Andrey>return (typeof window[function_name] == 'function');

Object-function may be defined as not a member of Window object.

#1. Steve Clay on 04 January 2008

Steve Clayreturn (typeof window[function_name] == 'function');