PHP's is_callable in JavaScript

How to use

You you can install via yarn add locutus and require this function via const is_callable = require('locutus/php/var/is_callable').

It is important to use a bundler that supports tree-shaking so that you only ship the functions that you actually use to your browser, instead of all of Locutus, which is massive. Examples are: Parcel, webpack, or rollup.js. For server-side use this is typically less of a concern.

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.

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

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.

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

module.exports = function is_callable(mixedVar, syntaxOnly, callableName) {
  //  discuss at: https://locutus.io/php/is_callable/
  // original by: Brett Zamir (https://brett-zamir.me)
  //    input by: François
  // improved by: Brett Zamir (https://brett-zamir.me)
  // improved by: KnightYoshi
  // improved by: Waldo Malqui Silva (https://fayr.us/waldo/)
  //      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
  //   example 5: is_callable(class MyClass {})
  //   returns 5: false

  const $global = typeof window !== 'undefined' ? window : global

  const validJSFunctionNamePattern = /^[_$a-zA-Z\xA0-\uFFFF][_$a-zA-Z0-9\xA0-\uFFFF]*$/

  let name = ''
  let obj = {}
  let method = ''
  let validFunctionName = false

  const getFuncName = function (fn) {
    const name = /\W*function\s+([\w$]+)\s*\(/.exec(fn)
    if (!name) {
      return '(Anonymous)'
    }
    return name[1]
  }

  // eslint-disable-next-line no-useless-escape
  if (/(^class|\(this\,)/.test(mixedVar.toString())) {
    return false
  }

  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
  }

  if (syntaxOnly || typeof obj[method] === 'function') {
    if (callableName) {
      $global[callableName] = name
    }
    return true
  }

  // validFunctionName avoids exploits
  // eslint-disable-next-line no-eval
  if (validFunctionName && typeof eval(method) === 'function') {
    if (callableName) {
      $global[callableName] = name
    }
    return true
  }

  return false
}

A community effort

Not unlike Wikipedia, Locutus is an ongoing community effort. Our philosophy follows The McDonald’s Theory. This means that we assimilate first iterations with imperfections, hoping for others to take issue with-and improve them. This unorthodox approach has worked very well to foster fun and fruitful collaboration, but please be reminded to use our creations at your own risk. THE SOFTWARE IS PROVIDED "AS IS" has never been more true than for Locutus.

Now go and: [ View on GitHub | Edit on GitHub | View Raw ]

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