In an array of objects fastest way to find the index of an object whose attributes match a search

Question

I ve been surfing around a little trying to find an efficient way to do this  but have gotten nowhere  I have an array of objects that looks like this   array i  id   some number  array i  name   some name    What i want to do is to find the INDEXES of the objects where id is equal to  for example  one of 0 1 2 3 or 4  I suppose I could just do something like    var indexes       for i 0  i lt array length  i         array i  id     0      indexes 0    i      array i  id     1      indexes 1    i      array i  id     2      indexes 2    i      array i  id     3      indexes 3    i      array i  id     4      indexes 4    i       While this would work  it looks to be quite expensive and slow  not to mention ugly   especially if array length could be large  Any ideas on how to spruce this up a bit  I thought of using array indexOf somehow but I don t see how to force the syntax  This  array indexOf this id     0     for example  returns undefined  as it probably should  Thanks in advance

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const index   array findIndex item   gt  item id      your-id     This should get you the index of item in array with id     your-id   x000D   x000D  array      id 1    id 2     x000D   x000D  const index   array findIndex item   gt  item id     2   x000D   x000D  console log index   x000D   x000D   x000D

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var indices       var IDs    0  1  2  3  4    for var i   0  len   array length  i  lt  len  i          for var j   0  j  lt  IDs length  j              if array i  id    ID  indices push i

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A new way using ES6  let picked element   array filter element   gt  element id     0

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I like this method because it s easy to compare to any value in the object no matter how deep it s nested     while i lt myArray length  amp  amp  myArray i  data value   value     i          i now hows the index value for the match    console log  Index - gt   i

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Maybe you would like to use higher-order functions such as  map   Assuming you want search by  field  attribute   var elementPos   array map function x   return x id     indexOf idYourAreLookingFor   var objectFound   array elementPos

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Since there s no answer using regular array find   var one    id  1  name   one    var two    id  2  name  two   var arr    one  two    var found   arr find  a    gt  a id     2   found     two    true  arr indexOf found     1

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The new Array method  filter   would work well for this   var filteredArray   array filter function  element         return element id     0        jQuery can also do this with  grep    edit  it is worth mentioning that both of these functions just iterate under the hood  there won t be a noticeable performance difference between them and rolling your own filter function  but why re-invent the wheel

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As I can t comment yet  I want to show the solution I used based on the method Umair Ahmed posted  but when you want to search for a key instead of a value      a  true     f  true     g  false    findIndex function element  return Object keys element  0      g       I understand that it doesn t answer the expanded question  but the title doesn t specify what was wanted from each object  so I want to humbly share this to save headaches to others in the future  while I undestart it may not be the fastest solution

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Sounds to me like you could create a simple iterator with a callback for testing  Like so   function findElements array  predicate        var matchingIndices            for var j   0  j  lt  array length  j                  if predicate array j               matchingIndices push j              return matchingIndices      Then you could invoke like so   var someArray            id  1  text   Hello            id  2  text   World            id  3  text   Sup            id  4  text   Dawg          var matchingIndices   findElements someArray  function item               return item id   2    0             Should have an array of  1  3  as the indexes that matched

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The simplest and easiest way to find element index in array   ES5 syntax    id 1   id 2   id 3   id 4   findIndex function obj  return obj id    3    ES6 syntax    id 1   id 2   id 3   id 4   findIndex obj   gt  obj id    3

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array forEach function  elem  i        iterate over all elements of array     indexes elem id    i               take the found id as index for the                                        indexes array and assign i   the result is a look up list for the id  with the given id we get the index of the record

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Adapting Tejs s answer for mongoDB and Robomongo I changed   matchingIndices push j     to  matchingIndices push NumberInt j 1

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To summary all of the great answer above and additional of my answer regarding find all the indexes occurred from some of the comment    To return the index of the first occurrence     x000D   x000D  const array      id  1      id  2      id  3      id  4      id  2     x000D  const idYourAreLookingFor   2  x000D   x000D    ES5  x000D    Output  1 x000D  array map function  x    return x id     indexOf idYourAreLookingFor   x000D   x000D    ES6  x000D    Output  1 x000D  array findIndex obj   gt  obj id     idYourAreLookingFor   x000D   x000D   x000D     To return the index array of all occurrences  using reduce     x000D   x000D  const array      id  1      id  2      id  3      id  4      id  2    x000D  const idYourAreLookingFor   2  x000D   x000D    ES5 x000D    Output   1  4  x000D  array reduce function  acc  obj  i    x000D    if  obj id     idYourAreLookingFor  x000D      acc push i   x000D    return acc  x000D          x000D   x000D    ES6 x000D    Output   1  4  x000D  array reduce  acc  obj  i    gt   obj id     idYourAreLookingFor    acc concat i    acc      x000D   x000D   x000D

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Using the ES6 map function   let idToFind   3  let index   someArray map obj   gt  obj id  indexOf idToFind

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var test        id 1  test  1      id 2  test  2      id 2  test  2      var result   test findIndex findIndex   2     console log result    function findIndex object      return object id    this      will return index 1  Works only in ES 2016

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If you care about performance  dont go with find or filter or map or any of the above discussed methods  Here is an example demonstrating the fastest method  HERE is the link to the actual test  Setup block  var items       for var i   0  i  lt  1000  i          items push  id  i   1      var find   523   Fastest Method  var index   -1 for var i   0  i  lt  items length  i          if items i  id     find            index   i          break            Slower Methods  items findIndex item   gt  item id     find    SLOWEST method  items map item   gt  item id  indexOf find

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I ve created a tiny utility called super-array where you can access items in an array by a unique identifier with O 1  complexity  Example   const SuperArray   require  super-array     const myArray   new SuperArray      id   ab1   name   John       id   ab2   name   Peter         console log myArray get  ab1         id   ab1   name   John   console log myArray get  ab2         id   ab2   name   Peter

[javascript] In an array of objects, fastest way to find the index of an object whose attributes match a search

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