How do I count a JavaScript object s attributes

Question

Suppose I have the following object in JavaScript   var object        key1    value1      key2    value2      key3    value3        How do I find out how many values exist in the object

User · Answer

This function makes use of Mozilla s   count   property if it is available as it is faster than iterating over every property   function countProperties obj      var count      count       hasOwnProp   Object prototype hasOwnProperty     if  typeof obj count       number   amp  amp   hasOwnProp call obj  count         return obj count         count   0    for  var prop in obj        if  hasOwnProp call obj  prop           count                return count      countProperties      1   2     3   4     5   6        3

User · Answer

EDIT  this will case errors with jquery to happen  plus some other inconveniences  YOU SHOULD NOT USE IT   perhaps if one could add a privaate method instead of a public property function  this would be OK  but don t have the time now   Community wikied  do not use   Even though javascript s object by default doesn t have the count function  classes are easily extendable  and one can add it oneself   Object prototype count   function          var count   0      for var prop in this            if this hasOwnProperty prop               count   count   1            return count      So that after that one can execute  var object     key1    val1    key2   val2    key3   val3    console log object count        3   As a conclusion  if you want count functionality in objects  you need to copy the code from code block 1  and paste it early in execution time   before you call the count     Let me know if that works for you   Regards  Pedro

User · Answer

You can do that by using this simple code   Object keys myObject  length

User · Answer

Use underscore library  very useful    keys obj  length

User · Answer

Although it wouldn t be a  true object   you could always do something like this   var foo        Key1   key1       Key2   key2       Key3   key3       alert foo length          3

User · Answer

There s no easy answer  because Object  mdash  which every object in JavaScript derives from  mdash  includes many attributes automatically  and the exact set of attributes you get depends on the particular interpreter and what code has executed before yours  So  you somehow have to separate the ones you defined from those you got  for free    Here s one way   var foo     key1    value1    key2    value2    key3    value3    Object prototype foobie    bletch      add property to foo that won t be counted  var count   0  for  var k in foo        if  foo hasOwnProperty k              count          alert  Found     count     properties specific to foo      The second line shows how other code can add properties to all Object derivatives  If you remove the hasOwnProperty   check inside the loop  the property count will go up to at least 4  On a page with other JavaScript besides this code  it could be higher than 4  if that other code also modifies the Object prototype

User · Answer

You can iterate over the object to get the keys or values   function numKeys obj        var count   0      for var prop in obj                count              return count     It looks like a  spelling mistake  but just want to point out that your example is invalid syntax  should bevar object     key1   value1   key2   value2   key3   value3

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var miobj         padreid   0    sw   0    dtip   UNO    datos           padreid   1    sw   0    dtip   DOS    datos           alert miobj length        2   but    alert miobj 0  length        undefined   this function is very good  Object prototype count   function          var count   0      for var prop in this            if this hasOwnProperty prop               count   count   1            return count     alert miobj count           2 alert miobj 0  count           4

User · Answer

For those which will read this question answers  here is a JavaScript implementation of Dictionary collection very similar as functionality as  NET one  JavaScript Dictionary

[javascript] How do I count a JavaScript object's attributes?

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