PHP's is_callable in JavaScript

Here’s what our current JavaScript equivalent to PHP's is_callable looks like.

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module.exports = function is_callable (mixedVar, syntaxOnly, callableName) { // eslint-disable-line camelcase
// discuss at: http://locutus.io/php/is_callable/
// original by: Brett Zamir (http://brett-zamir.me)
// input by: François
// improved by: Brett Zamir (http://brett-zamir.me)
// note 1: The variable callableName cannot work as a string variable passed by
// note 1: reference as in PHP (since JavaScript does not support passing
// note 1: strings by reference), but instead will take the name of
// note 1: a global variable and set that instead.
// note 1: When used on an object, depends on a constructor property
// note 1: being kept on the object prototype
// note 2: Depending on the `callableName` that is passed, this function can use eval.
// note 2: The eval input is however checked to only allow valid function names,
// note 2: So it should not be unsafer than uses without eval (seeing as you can)
// note 2: already pass any function to be executed here.
// example 1: is_callable('is_callable')
// returns 1: true
// example 2: is_callable('bogusFunction', true)
// returns 2: true // gives true because does not do strict checking
// example 3: function SomeClass () {}
// example 3: SomeClass.prototype.someMethod = function (){}
// example 3: var testObj = new SomeClass()
// example 3: is_callable([testObj, 'someMethod'], true, 'myVar')
// example 3: var $result = myVar
// returns 3: 'SomeClass::someMethod'
// example 4: is_callable(function () {})
// returns 4: true
var $global = (typeof window !== 'undefined' ? window : global)
var validJSFunctionNamePattern = /^[_$a-zA-Z\xA0-\uFFFF][_$a-zA-Z0-9\xA0-\uFFFF]*$/
var name = ''
var obj = {}
var method = ''
var validFunctionName = false
var getFuncName = function (fn) {
var name = (/\W*function\s+([\w$]+)\s*\(/).exec(fn)
if (!name) {
return '(Anonymous)'
}
return name[1]
}
if (typeof mixedVar === 'string') {
obj = $global
method = mixedVar
name = mixedVar
validFunctionName = !!name.match(validJSFunctionNamePattern)
} else if (typeof mixedVar === 'function') {
return true
} else if (Object.prototype.toString.call(mixedVar) === '[object Array]' &&
mixedVar.length === 2 &&
typeof mixedVar[0] === 'object' &&
typeof mixedVar[1] === 'string') {
obj = mixedVar[0]
method = mixedVar[1]
name = (obj.constructor && getFuncName(obj.constructor)) + '::' + method
} else {
return false
}
if (syntaxOnly || typeof obj[method] === 'function') {
if (callableName) {
$global[callableName] = name
}
return true
}
// validFunctionName avoids exploits
if (validFunctionName && typeof eval(method) === 'function') { // eslint-disable-line no-eval
if (callableName) {
$global[callableName] = name
}
return true
}
return false
}
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How to use

You you can install via npm install locutus and require it via require('locutus/php/var/is_callable'). You could also require the var module in full so that you could access var.is_callable instead.

If you intend to target the browser, you can then use a module bundler such as Browserify, webpack or rollup.js.

ES5/ES6

This function targets ES5, but as of Locutus 2.0.2 we also support ES6 functions. Locutus transpiles to ES5 before publishing to npm.

A community effort

Not unlike Wikipedia, Locutus is an ongoing community effort. Our philosophy follows The McDonald’s Theory. This means that we don't consider it to be a bad thing that many of our functions are first iterations, which may still have their fair share of issues. We hope that these flaws will inspire others to come up with better ideas.

This way of working also means that we don't offer any production guarantees, and recommend to use Locutus inspiration and learning purposes only.

Notes

  • The variable callableName cannot work as a string variable passed by reference as in PHP (since JavaScript does not support passing strings by reference), but instead will take the name of a global variable and set that instead. When used on an object, depends on a constructor property being kept on the object prototype

  • Depending on the callableName that is passed, this function can use eval. The eval input is however checked to only allow valid function names, So it should not be unsafer than uses without eval (seeing as you can) already pass any function to be executed here.

Examples

Please note that these examples are distilled from test cases that automatically verify our functions still work correctly. This could explain some quirky ones.

#codeexpected result
1is_callable('is_callable')true
2is_callable('bogusFunction', true)true // gives true because does not do strict checking
3function SomeClass () {} SomeClass.prototype.someMethod = function (){} var testObj = new SomeClass() is_callable([testObj, 'someMethod'], true, 'myVar') var $result = myVar'SomeClass::someMethod'
4is_callable(function () {})true

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