How to display all methods of an object

Question

I want to know how to list all methods available for an object like for example    alert show all methods Math      This should print    abs  acos  asin  atan  atan2  ceil  cos  exp  floor  log  max  min  pow  random round  sin  sqrt  tan

User · Answer

var methods       for  var m in obj        if  typeof obj m      function             methods push m           alert methods join          This way  you will get all methods that you can call on obj  This includes the methods that it  inherits  from its prototype  like getMethods   in java   If you only want to see those methods defined directly by obj you can check with hasOwnProperty   var methods       for  var m in obj                if  typeof obj m      function   amp  amp  obj hasOwnProperty m             methods push m           alert methods join

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Most modern browser support console dir obj   which will return all the properties of an object that it inherited through its constructor   See Mozilla s documentation for more info and current browser support   console dir Math    gt  MathConstructor E  2 718281828459045 LN2  0 6931471805599453     tan  function tan      native code      proto    Object

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The other answers here work for something like Math  which is a static object  But they don t work for an instance of an object  such as a date  I found the following to work   function getMethods o      return Object getOwnPropertyNames Object getPrototypeOf o        filter m   gt   function      typeof o m       example  getMethods new Date         getFullYear    setMonth           https   jsfiddle net 3xrsead0   This won t work for something like the original question  Math   so pick your solution based on your needs  I m posting this here because Google sent me to this question but I was wanting to know how to do this for instances of objects

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Math has static method where you can call directly like Math abs   while Date has static method like Date now   and also instance method where you need to create new instance first var time   new Date   to call time getHours        The instance method of Date can be found on  Date prototype  so you can just call  var keys   Object getOwnPropertyNames Date prototype       And for the static method var keys   Object getOwnPropertyNames Date       But if the instance already created you need to    pass its constructor var time   new Date    var staticKeys   Object getOwnPropertyNames time constructor   var instanceKeys   Object getOwnPropertyNames time constructor prototype     Of course you will need to filter the obtained keys for the static method to get actual method names  because you can also get length  name that aren t a function on the list   But how if we want to obtain all available method from class that extend another class  Of course you will need to scan through the root of prototype like using   proto    For saving your time you can use script below to get static method and deep method instance    x000D   x000D     var keys   new Set    x000D  function getStaticMethods keys  clas   x000D      var keys2   Object getOwnPropertyNames clas   x000D   x000D      for var i   0  i  lt  keys2 length  i     x000D          if clas keys2 i   constructor     Function  x000D              keys add keys2 i    x000D        x000D    x000D   x000D  function getPrototypeMethods keys  clas   x000D      if clas prototype     void 0  x000D          return  x000D   x000D      var keys2   Object getOwnPropertyNames clas prototype   x000D      for  var i   keys2 length - 1  i  gt   0  i--    x000D          if keys2 i       constructor   x000D              keys add keys2 i    x000D        x000D   x000D      var deep   Object getPrototypeOf clas   x000D      if deep prototype     void 0  x000D          getPrototypeMethods keys  deep   x000D    x000D   x000D            Usage example        x000D     To avoid duplicate on deeper prototype we use  Set  x000D  var keys   new Set    x000D  getStaticMethods keys  Date   x000D  getPrototypeMethods keys  Date   x000D   x000D  console log Array from keys    x000D   x000D   x000D    If you want to obtain methods from created instance  don t forget to pass the constructor of it

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It s not possible with ES3 as the properties have an internal DontEnum attribute which prevents us from enumerating these properties  ES5  on the other hand  provides property descriptors for controlling the enumeration capabilities of properties so user-defined and native properties can use the same interface and enjoy the same capabilities  which includes being able to see non-enumerable properties programmatically   The getOwnPropertyNames function can be used to enumerate over all properties of the passed in object  including those that are non-enumerable  Then a simple typeof check can be employed to filter out non-functions  Unfortunately  Chrome is the only browser that it works on currently    function getAllMethods object        return Object getOwnPropertyNames object  filter function property            return typeof object property      function              console log getAllMethods Math      logs   cos    pow    log    tan    sqrt    ceil    asin    abs    max    exp    atan2    random    round    floor    acos    atan    min    sin   in no particular order

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I believe there s a simple historical reason why you can t enumerate  over methods of built-in objects like Array for instance  Here s why   Methods are properties of the prototype-object  say Object prototype  That means that all Object-instances will inherit those methods  That s why you can use those methods on any object  Say  toString   for instance   So IF methods were enumerable  and I would iterate over say  a 123  with     for  key in  a 123           what would happen  How many times  would that loop be executed    It would be iterated once for the single key  a  in our example  BUT ALSO once for every enumerable property of Object prototype  So if methods were enumerable  by default   then any loop over any object would loop  over all its inherited methods as well

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You can use Object getOwnPropertyNames   to get all properties that belong to an object  whether enumerable or not   For example   console log Object getOwnPropertyNames Math      - gt    E    LN10    LN2    LOG2E    LOG10E    PI      etc     You can then use filter   to obtain only the methods   console log Object getOwnPropertyNames Math  filter function  p        return typeof Math p       function          - gt    random    abs    acos    asin    atan    ceil    cos    exp      etc       In ES3 browsers  IE 8 and lower   the properties of built-in objects aren t enumerable   Objects like window and document aren t built-in  they re defined by the browser and most likely enumerable by design   From ECMA-262 Edition 3      Global Object   There is a unique global   object  15 1   which is created before   control enters any execution context    Initially the global object has the   following properties             Built-in   objects such as Math  String  Date    parseInt  etc  These have attributes     DontEnum          Additional host defined   properties  This may include a   property whose value is the global   object itself  for example  in the   HTML document object model the window   property of the global object is the   global object itself         As control   enters execution contexts  and as   ECMAScript code is executed    additional properties may be added to   the global object and the initial   properties may be changed    I should point out that this means those objects aren t enumerable properties of the Global object   If you look through the rest of the specification document  you will see most of the built-in properties and methods of these objects have the   DontEnum   attribute set on them     Update  a fellow SO user  CMS  brought an IE bug regarding   DontEnum   to my attention      Instead of checking the DontEnum attribute   Microsoft  JScript will skip over any property in any object where there is a same-named property in the object s prototype chain that has the attribute DontEnum    In short  beware when naming your object properties   If there is a built-in prototype property or method with the same name then IE will skip over it when using a for   in loop

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The short answer is you can t because Math and Date  off the top of my head  I m sure there are others  are t normal objects   To see this  create a simple test script    lt html gt     lt body gt       lt script type  text javascript  src  http   ajax googleapis com ajax libs jquery 1 4 1 jquery min js  gt  lt  script gt       lt script type  text javascript  gt          function             alert  Math      Math           alert  Math      Math sqrt           alert  Date      Date           alert  Array      Array           alert  jQuery      jQuery           alert  Document      document           alert  Document      document ready                  lt  script gt     lt  body gt   lt  html gt    You see it presents as an object the same ways document does overall  but when you actually try and see in that object  you see that it s native code and something not exposed the same way for enumeration

[javascript] How to display all methods of an object?

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