JavaScript function_exists
Checks if the function exists
1 2 3 4 56 7 8 9 1011 12 13 14 1516 | function function_exists (func_name) { // Checks if the function exists // // version: 1109.2015 // discuss at: http://phpjs.org/functions/function_exists // + original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net) // + improved by: Steve Clay // + improved by: Legaev Andrey // + improved by: Brett Zamir (http://brett-zamir.me) // * example 1: function_exists('isFinite'); // * returns 1: true if (typeof func_name === 'string') { func_name = this.window[func_name]; } return typeof func_name === 'function';} |
Examples
Running
1 | function_exists('isFinite'); |
Should return
1 | true |
Dependencies
No dependencies, you can use this function standalone.
Open syntax issues
php.js uses JsLint to help us keep our code consistent and prevent some common bugs.
Eventually we want all code to pass or at least take into consideration most fixes suggested by JsLint, following this JsLint configuration we’ve decided on.
Authors
Thanks to the following developers, you get to have function_exists goodness in JavaScript.
Brett Zamir
6 Aug '11 
I assume the compiler might be looking for the text "function_name", so I changed that variable name in the function as a workaround. See if that works...
Bug in function_exists
5 Aug '11
Hi guys
Firstly thanks for a great little script!
I am a php programmer and having phpjs is great!
I downloaded the latest version of phpjf and found a bug with the function_exists() function.
When it is compiled the function definition looks like this
function_exists: function (_name: function) {
which causes an error.
I don't think its an actual bug in the code, its just in the compilation of the package :)
Thanks again guys
Have a great day
Kevin van Zonneveld
30 Dec '08
@ Brett Zamir: Thanks Brett. I've added the functions. I do have the idea they could be standardized & improved a bit though, but I'll leave that up to the 'future us' :) Let those guys handle it.
Seriously though: I think the class_exists example I've made should return true, but it doesn't. That's a good one to start with.
Brett Zamir
23 Dec '08
Added one last condition which will find if there is a static members on the class to which an object belongs, as well as some example tests for it as well:
[CODE="Javascript"]myClass2.prototype.instanceMethod = function () {}
myClass2.prototype.mine = 'my member';
var_dump(property_exists(new myClass2, 'mine')); //true
var_dump(property_exists(new myClass2, 'xpto')); //true, as of PHP 5.3.0
var_dump(property_exists(new myClass2, 'bar')); //false
var_dump(property_exists(new myClass2, 'staticProp')); //true, as of PHP 5.3.0
var_dump(property_exists(new myClass2, 'staticMethod')); //false
var_dump(property_exists(new myClass2, 'instanceMethod')); //false
var myclass2 = new myClass2();
myclass2.staticMethod(); // doesn't exist
[/CODE]
[CODE="Javascript"]function property_exists (cls, prop) {
cls = (typeof cls === 'string') ? window[cls] : cls;
if (typeof cls === 'function' && cls.toSource && cls.toSource().match(new RegExp('this\\.'+prop+'\\s'))) { // Hackish and non-standard but can probably detect if setting the property (we don't want to test by instantiating as that may have side-effects)
return true;
}
return (cls[prop] !== undefined && typeof cls[prop] !== 'function') || (cls.prototype !== undefined && cls.prototype[prop] !== undefined && typeof cls.prototype[prop] !== 'function') || cls.constructor && cls.constructor[prop] !== undefined && typeof cls.constructor[prop] !== 'function';
}[/CODE]
Brett Zamir
23 Dec '08
And here's one for property_exists(), based on PHP doc examples:
[CODE="Javascript"]var myClass = {
mine : {},
xpto : {},
test : function () {
var_dump(property_exists('myClass', 'xpto')); // true
}
}
var_dump(property_exists('myClass', 'mine')); //true
var_dump(property_exists('myClass', 'xpto')); //true
var_dump(property_exists('myClass', 'bar')); //false
var_dump(property_exists('myClass', 'test')); // false (PHP considers methods as distinct from properties)
myClass.test(); // true
function myClass2 () {
this.xpto = 'something';
}
myClass2.staticProp = 'staticValue';
myClass2.staticMethod = function () {
var_dump(property_exists('myClass2', 'xpto')); // true
}
myClass2.prototype.instanceMethod = function () {}
myClass2.prototype.mine = 'my member';
var_dump(property_exists('myClass2', 'mine')); //true
var_dump(property_exists(new myClass2, 'mine')); //true
var_dump(property_exists('myClass2', 'xpto')); //true, as of PHP 5.3.0
var_dump(property_exists('myClass2', 'bar')); //false
var_dump(property_exists('myClass2', 'staticProp')); //true, as of PHP 5.3.0
var_dump(property_exists('myClass2', 'staticMethod')); //false
var_dump(property_exists('myClass2', 'instanceMethod')); //false
myClass2.staticMethod(); // true
function property_exists (cls, prop) {
cls = (typeof cls === 'string') ? window[cls] : cls;
if (typeof cls === 'function' && cls.toSource && cls.toSource().match(new RegExp('this\\.'+prop+'\\s'))) { // Hackish and non-standard but can probably detect if setting the property (we don't want to test by instantiating as that may have side-effects)
return true;
}
return (cls[prop] !== undefined && typeof cls[prop] !== 'function') || (cls.prototype !== undefined && cls.prototype[prop] !== undefined && typeof cls.prototype[prop] !== 'function');
}
[/CODE]
Brett Zamir
23 Dec '08
Here's a slightly hackish and partially non-standard way to get class_exists(). Of course, any function can be instantiated in JavaScript, but I've attempted to do a hopefully more sophisticated checking to see whether it was designed as one.
[CODE="Javascript"]
function A (z) {this.z=z}
alert(class_exists('A')); // true (constructor sets 'this')
var a = new A('str');
alert(class_exists('a')); // false (objects not classes)
function B () {}
B.c = function () {}; // Add a static method, making it a class
alert(class_exists('B')); // true
function C () {}
C.prototype.z = function () {};
alert(class_exists('C')); // true
function D (b) {}
alert(class_exists('D')); // false (seems like a regular function)
var e = {
E : function (z) {this.z=z;}
}
alert(class_exists('e.E')); // false (the 'this' refers to containing object, not to an instance property)
function class_exists (cls) {
cls = window[cls]; // Note: will prevent inner classes
if (typeof cls !== 'function') {return false;}
for (var i in cls.prototype) {
return true;
}
for (var i in cls) { // If static members exist, then consider a "class"
if (i !== 'prototype') {
return true;
}
}
if (cls.toSource && cls.toSource().match(/this\./)) { // Hackish and non-standard but can probably detect if setting a property (we don't want to test by instantiating as that may have side-effects)
return true;
}
return false;
}[/CODE]
Brett Zamir
23 Dec '08
Fixing an error and adding more examples:
[CODE="Javascript"]function Directory () {}
Directory.test = function () {}
Directory.prototype.read = function () {}
$directory = new Directory('.');
alert(true === method_exists($directory,'read')); // true
alert(true === method_exists($directory,'write')); // false
alert(true === method_exists('Directory','test')); // true
alert(true === method_exists('Directory','read')); // false
alert(true === method_exists($directory,'test')); // false
function method_exists (obj, method) {
if (typeof obj === 'string') {
return window[obj] && typeof window[obj][method] === 'function'
}
return typeof obj[method] === 'function';
}
[/CODE]
Brett Zamir
20 Dec '08
Sorry, neglected to see a string was allowable to test for a static method:
[CODE="Javascript"]
function Directory () {}
Directory.test = function () {}
Directory.prototype.read = function () {}
$directory = new Directory('.');
alert(true === method_exists($directory,'read')); // true
alert(true === method_exists($directory,'write')); // false
alert(true === method_exists('Directory','test')); // true
[/CODE]
[CODE="Javascript"]function method_exists (obj, method) {
if (typeof obj === 'string') {
return typeof window[obj][method] === 'function'
}
return typeof obj[method] === 'function';
}[/CODE]
Brett Zamir
20 Dec '08
Here's another one more related to the function here...
Sample based on PHP manual...
[CODE="Javascript"]function Directory () {}
Directory.prototype.read = function () {}
$directory = new Directory('.');
alert(true === method_exists($directory,'read')); // true
alert(true === method_exists($directory,'write')); // false
[/CODE]
[CODE="Javascript"]function method_exists (obj, method) {
return typeof obj[method] === 'function';
}[/CODE]
Arignmor
9 Nov '11