indexOf method in an object array

Question

What s the best method to get the index of an array which contains objects   Imagine this scenario   var hello         hello   world       foo   bar     var qaz         hello   stevie       foo   baz     var myArray       myArray push hello qaz     Now I would like to have the indexOf the object which hello property is  stevie  which  in this example  would be 1   I m pretty newbie with JavaScript and I don t know if there is a simple method or if I should build my own function to do that

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See this example  http   jsfiddle net 89C54   for  i   0  i  lt  myArray length  i          if  myArray i  hello      stevie             alert  position      i           return            It starts to count with zero

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I did some performance testing of various answers here  which anyone can run them self   https   jsperf com find-index-of-object-in-array-by-contents  Based on my initial tests in Chrome  the following method  using a for loop set up inside a prototype  is the fastest   Array prototype indexOfObject   function  property  value        for  var i   0  len   this length  i  lt  len  i              if  this i  property      value  return i            return -1     myArray indexOfObject  hello    stevie      This code is a slightly modified version of Nathan Zaetta s answer   In the performance benchmarks I tried it with both the target being in the middle  index 500  and very end  index 999  of a 1000 object array  and even if I put the target in as the very last item in the array  meaning that it it has to loop through every single item in the array before it s found  it still ends up the fastest   This solution also has the benefit of being one of the most terse for repeatedly executing  since only the last line needs to be repeated   myArray indexOfObject  hello    stevie

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If you are only interested into finding the position see  Pablo s answer   pos   myArray map function e    return e hello     indexOf  stevie     However  if you are looking forward to finding the element  i e  if you were thinking of doing something like this myArray pos    there is a more efficient one-line way to do it  using filter   element   myArray filter  e    gt  e hello      stevie   0    See perfomance results     42  ops sec   http   jsbench github io  7fa01f89a5dc5cc3bee79abfde80cdb3

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array filter function item  indx  arr   return item hello      stevie       0     Mind the  0    It is proper to use reduce as in Antonio Laguna s answer   Apologies for the brevity

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I like Pablo s answer  but Array indexOf and Array map don t work on all browsers  Underscore will use native code if it s available  but has fallbacks as well  Plus it has the pluck method for doing exactly what Pablo s anonymous map method does   var idx     chain myArray  pluck  hello   indexOf  Stevie   value

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Using the ES6 findIndex method  without lodash or any other libraries  you can write   function deepIndexOf arr  obj      return arr findIndex function  cur        return Object keys obj  every function  key          return obj key      cur key                     This will compare the immediate properties of the object  but not recurse into the properties   If your implementation doesn t provide findIndex yet  most don t   you can add a light polyfill that supports this search   function deepIndexOf arr  obj      function findIndex   Array prototype findIndex    function  pred        for  let i   0  i  lt  this length    i          if  pred call this  this i   i             return i                     return -1         return findIndex call arr  function  cur        return Object keys obj  every function  key          return obj key      cur key                      from my answer on this dupe

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var hello    hello   world    foo   bar    var qaz    hello   stevie   foo   baz    var myArray       myArray push hello qaz    function indexOfObject  arr  key  value           var j   -1      var result   arr some function obj  i             j            return obj key     value              if   result            return -1        else           return j            alert indexOfObject myArray  hello   world

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Brief  myArray indexOf  stevie   hello     Use Cases            NORMAL         2 4 5  indexOf 4     OUTPUT 1       COMPLEX          slm 2   slm 4   slm 5   indexOf 4  slm     OUTPUT 1    OR    slm 2   slm 4   slm 5   indexOf 4 function e i      return e slm       OUTPUT 1     MORE Complex      slm  salat 2    slm  salat 4    slm  salat 5    indexOf 4 function e i      return e slm salat       OUTPUT 1   API        Array prototype indexOfOld Array prototype indexOf      Array prototype indexOf function e fn         if  fn  return this indexOfOld e         else          if typeof fn     string   var att fn fn function e  return e att             return this map fn  indexOfOld e

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This is the way to find the object s index in array      var myArray       hello   world           foo   bar                  hello   stevie           foo   baz                 for  i   0  i  lt  myArray length  i              if  myArray i  hello      stevie                 alert  position      i               return

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I have made a generic function to check the below is the code  amp  works for any object  function indexOfExt list  item        var len   list length       for  var i   0  i  lt  len  i              var keys   Object keys list i            var flg   true          for  var j   0  j  lt  keys length  j                  var value   list i  keys j                if  item keys j       value                    flg   false                                  if  flg    true                return i                      return -1     var items       hello    world    foo    bar      var selectedItem      hello    world    foo    bar     alert items indexOf selectedItem    alert indexOfExt items  selectedItem      The first alert will return -1  means match not found   amp  second alert will return 0  means match found

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Array prototype findIndex is supported in all browsers other than IE  non-edge   But the polyfill provided is nice   var indexOfStevie   myArray findIndex i   gt  i hello      stevie      The solution with map is okay  But you are iterating over the entire array every search  That is only the worst case for findIndex which stops iterating once a match is found    There s not really a concise way  when devs had to worry about IE8   but here s a common solution   var searchTerm    stevie       index   -1  for var i   0  len   myArray length  i  lt  len  i          if  myArray i  hello     searchTerm            index   i          break            or as a function   function arrayObjectIndexOf myArray  searchTerm  property        for var i   0  len   myArray length  i  lt  len  i              if  myArray i  property      searchTerm  return i            return -1    arrayObjectIndexOf arr   stevie    hello       1   Just some notes    Don t use for   in loops on arrays Be sure to break out of the loop or return out of the function once you ve found your  needle  Be careful with object equality   For example   var a    obj  0   var b    a   b indexOf  obj  0       -1 not found

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I compared several methods and received a result with the fastest way to solve this problem  It s a for loop  It s 5  times faster than any other method     Here is the test s page  https   jsbench me 9hjewv6a98

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You can create your own prototype to do this   something like    Array prototype indexOfObject   function  object        for  var i   0  i  lt  this length  i              if  JSON stringify this i       JSON stringify object               return i

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You can simply use    x000D   x000D  const someId   2  x000D  const array     id 1    id 2    id 3    x000D  const index   array reduce  i  item  index    gt  item id     someId   index   i  -1   x000D  alert  someId     someId     is at index     index   x000D   x000D   x000D    No underscore  no for  just a reduce

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You can use a native and convenient function Array prototype findIndex   basically      The findIndex   method returns an index in the array  if an element in the array satisfies the provided testing function  Otherwise -1 is returned    Just a note it is not supported on Internet Explorer  Opera and Safari  but you can use a Polyfill provided in the link below   More information   https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Array findIndex   x000D   x000D  var hello     x000D    hello   world   x000D    foo   bar  x000D     x000D  var qaz     x000D    hello   stevie   x000D    foo   baz  x000D    x000D   x000D  var myArray       x000D  myArray push hello  qaz   x000D   x000D  var index   myArray findIndex function element  index  array    x000D    if  element hello      stevie     x000D      return true  x000D      x000D      x000D  alert  stevie is at index      index   x000D   x000D   x000D

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Try this   console log Object keys  foo   0    bar   1     indexOf  bar       https   developer mozilla org en docs Web JavaScript Reference Global Objects Object keys

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In ES2015  this is pretty easy   myArray map x   gt  x hello  indexOf  stevie     or  probably with better performance for larger arrays   myArray findIndex x   gt  x hello      stevie

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While  most other answers here are valid  Sometimes  it s best to just make a short simple function near where you will use it       indexOf wrapper for the list of objects function indexOfbyKey obj list  key  value        for  index in obj list            if  obj list index  key      value  return index            return -1       Find the string in the list  default -1  var test1   indexOfbyKey object list   name    Stevie    var test2   indexOfbyKey object list   last name    some other name      It depends on what is important to you  It might save lines of code and be very clever to use a one-liner  or to put a generic solution somewhere that covers various edge cases  But sometimes it s better to just say   here I did it like this  rather than leave future developers to have extra reverse engineering work  Especially if you consider yourself  a newbie  like in your question

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Or prototype it    Array prototype indexOfObject   function arrayObjectIndexOf property  value        for  var i   0  len   this length  i  lt  len  i              if  this i  property      value  return i            return -1     myArr indexOfObject  name    stevie

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Furthor of  Monika Garg answer  you can use findIndex    There is a polyfill for unsupprted browsers    I saw that people downvoted this answer  and I hope that they did this because of the wrong syntax  because on my opinion  this is the most elegant way      The findIndex   method returns an index in the array  if an element in the array satisfies the provided testing function  Otherwise -1 is returned    For example     x000D   x000D  var hello     x000D    hello   world   x000D    foo   bar  x000D     x000D  var qaz     x000D    hello   stevie   x000D    foo   baz  x000D    x000D   x000D  var myArray       x000D  myArray push hello qaz   x000D   x000D  var index   myArray findIndex function element    x000D    return element hello     stevie   x000D      x000D   x000D  alert index   x000D   x000D   x000D

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var idx   myArray reduce  function  cur  val  index         if  val hello      stevie   amp  amp  cur     -1             return index            return cur      -1

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I will prefer to use findIndex   method    var index   myArray findIndex  hello   stevie      index will give you the index number

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simple   myArray indexOf myArray filter function item        return item hello     stevie     0

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This works without custom code  var arr  a  found  arr     x  1  y  2    a    x  1  y  2   found   JSON stringify arr  indexOf JSON stringify a    gt  - 1     found     true      Note  this does not give the actual index  it only tells if your object exists in the current data structure

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Use   findIndex from underscore js library   Here s the example   findIndex   a 1   a  2 c 10   a  3     a 2 c 10     1

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I think you can solve it in one line using the map function   pos   myArray map function e    return e hello     indexOf  stevie

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If your object is the same object of the ones you are using within the array  you should be able to get the index of the Object in the same way you do as if it was a string   var hello         hello   world       foo   bar     var qaz         hello   stevie       foo   baz     var qazCLONE        new object instance and same structure     hello   stevie       foo   baz     var myArray    hello qaz    myArray indexOf qaz     should return 1 myArray indexOf qazCLONE     should return -1

[javascript] indexOf method in an object array?

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