How to check if array element exists or not in javascript

Question

I am working with Titanium  my code looks like this   var currentData   new Array     if currentData index        currentData index    null  currentData index     null         Ti API info  is exists      currentData index        return true    else          return false      I am passing an index to the array currentData  I am still not able to detect a non-existing element using above code

User · Answer

Consider the array a   var a    name1  1   name2  2    If you want to check if  name1  exists in a  simply test it with in   if  name1  in a   console log  name1 exists in a    else console log  name1 is not in a

User · Answer

var demoArray     A   B   C   D    var ArrayIndexValue   2  if ArrayIndexValue in demoArray        Array index exists  else       Array Index does not Exists

User · Answer

This way is easiest one in my opinion   var nameList   new Array  item1   item2   item3   item4        Using for loop to loop through each item to check if item exist   for  var i   0  i  lt  nameList length  i      if  nameList i       item1            alert  Value exist     else     alert  Value doesn  t exist        And Maybe Another way to do it is   nameList forEach function ItemList        if ItemList name     item1                       alert  Item Exist

User · Answer

Someone please correct me if i m wrong  but AFAIK the following is true    Arrays are really just Objects under the hood of JS  Thus  they have the prototype method hasOwnProperty  inherited  from Object in my testing  hasOwnProperty can check if anything exists at an array index    So  as long as the above is true  you can simply   const arrayHasIndex    array  index    gt  Array isArray array   amp  amp  array hasOwnProperty index    usage   arrayHasIndex  1 2 3 4  4   outputs  false  arrayHasIndex  1 2 3 4  2   outputs  true

User · Answer

x000D   x000D  var fruits     Banana    Orange    Apple    Mango    x000D  if fruits indexOf  Banana      -1   x000D      console log  item not exist   x000D    else   x000D   console log  item exist   x000D    x000D   x000D   x000D

User · Answer

you can simply use this    var tmp     a    b    index   3   if  tmp index        console log tmp index      n     else      console log   does not exist

User · Answer

This is exactly what the in operator is for  Use it like this   if  index in currentData          Ti API info index     exists      currentData index        The accepted answer  is wrong  it will give a false negative if the value at index is undefined    x000D   x000D  const currentData     a   undefined   index   1  x000D   x000D  if  index in currentData    x000D    console info  exists    x000D    x000D        vs    x000D  if  typeof currentData index       undefined     x000D    console info  exists    x000D    else   x000D    console info  does not exist       incorrect  x000D    x000D   x000D   x000D

User · Answer

Simple way to check item exist or not  Array prototype contains   function obj        var i   this length      while  i--         if  this i     obj         return true      return false     var myArray    Banana    Orange    Apple    Mango     myArray contains  Apple

User · Answer

This also works fine  testing by type against undefined    if  currentData index      undefined  return    Test    x000D   x000D  const fruits     Banana    Orange    Apple    Mango    x000D   x000D  if  fruits  Raspberry       undefined   x000D    console log  No Raspberry entry in fruits    x000D    x000D   x000D   x000D

User · Answer

When trying to find out if an array index exists in JS  the easiest and shortest way to do it is through double negation   let a       a 1     foo   console log   a 0        false console log   a 1        true

User · Answer

var myArray     Banana    Orange    Apple    Mango     if  myArray indexOf searchTerm      -1      console log  element doesn t exist      else     console log  element found

User · Answer

If you use underscore js then these type of null and undefined check are hidden by the library   So your code will look like this -  var currentData   new Array     if    isEmpty currentData   return false   Ti API info  is exists      currentData index     return true    It looks much more readable now

User · Answer

If elements of array are also simple objects or arrays  you can use some function      search object var element     item  book   title  javasrcipt        item  handbook   title  c        item  book   title  javasrcipt    some function el       if  el item     element item  amp  amp  el title     element title            return true                   handbook    c        book    javasrcipt    some function el       if el 0     element item  amp  amp  el 1     element title           return true

User · Answer

If you are looking for some thing like this   Here is the following snippetr   x000D   x000D  var demoArray     A   B   C   D    x000D  var ArrayIndexValue   2  x000D  if demoArray includes ArrayIndexValue    x000D  alert  value exists    x000D       Array index exists x000D   else  x000D  alert  does not exist    x000D       Array Index does not Exists x000D    x000D   x000D   x000D

User · Answer

typeof files 1      undefined               this props upload  file  files                this props postMultipleUpload  file  files widgetIndex  0  id     Check if the second item in the array is undefined using the typeof and checking for undefined

User · Answer

I had to wrap techfoobar s answer in a try  catch block  like so   try     if typeof arrayName index      undefined            does not exist       else        does exist        catch  error      ignore           that s how it worked in chrome  anyway  otherwise  the code stopped with an error

User · Answer

const arr       typeof arr 0      undefined   arr 0     undefined   If boolean expression  typeof arr 0      typeof undefined   is true then 0 is contained in arr

User · Answer

Use typeof arrayName index       undefined   i e   if typeof arrayName index       undefined            does not exist   else          does exist

[javascript] How to check if array element exists or not in javascript?

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