How to get index of object by its property in JavaScript

Question

For example  I have   var Data         id list  1  name   Nick   token   312312         id list  2  name   John   token   123123         Then  I want to sort reverse this object by name  for example  And then I want to get something like this   var Data         id list  2  name   John   token   123123         id list  1  name   Nick   token   312312         And now I want to know the index of the object with property name  John  to get the value of the property token   How do I solve the problem

User · Answer

Using underscore   var index     indexOf   pluck item    name     Nick

User · Answer

What about this      Data indexOf   find Data  function element      return element name      John          Assuming you are using lodash or underscorejs

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Why don t you use a small work-around   Create a new array with names as indexes  after that all searches will use indexes  So  only one loop  After that you don t need to loop through all elements   var Data          id list 1  name  Nick  token  312312    id list 2 name  John  token  123123         var searchArr      Data forEach function one     searchArr one name  one     console log searchArr  Nick      http   jsbin com xibala 1 edit  live example

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collection findIndex item   gt  item value      smth       -1

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You can use Array sort using a custom function as parameter to define your sorting mecanism   In your example  it would give     var Data          id list 1  name  Nick  token  312312    id list 2 name  John  token  123123      Data sort function a  b       return a name  lt  b name   -1   a name  gt  b name   1   0       alert  First name is       Data 0  name      alerts  John  alert  Second name is       Data 1  name      alerts  Nick    The sort function must return either -1 if a should come before b  1 if a should come after b and 0 if both are equal  It s up to you to define the right logic in your sorting function to sort the array   Edit   Missed the last part of your question where you want to know the index  You would have to loop through the array to find that as others have said

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a prototypical way   function      if   Array prototype indexOfPropertyValue       Array prototype indexOfPropertyValue   function prop value         for  var index   0  index  lt  this length  index             if  this index  prop              if  this index  prop     value               return index                                      return -1                       usage   var Data       id list 1  name  Nick  token  312312    id list 2 name  John  token  123123      Data indexOfPropertyValue  name   John       returns 1  index of array    Data indexOfPropertyValue  name   Invalid name      returns -1  no result    var indexOfArray   Data indexOfPropertyValue  name   John     Data indexOfArray     returns desired object

User · Answer

As the other answers suggest  looping through the array is probably the best way  But I would put it in it s own function  and make it a little more abstract   function findWithAttr array  attr  value        for var i   0  i  lt  array length  i    1            if array i  attr      value                return i                      return -1     var Data          id list  2  name   John   token   123123         id list  1  name   Nick   token   312312        With this  not only can you find which one contains  John  but you can find which contains the token  312312    findWithAttr Data   name    John       returns 0 findWithAttr Data   token    312312       returns 1 findWithAttr Data   id list    10       returns -1   EDIT  Updated function to return -1 when not found so it follows the same construct as Array prototype indexOf

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Extended Chris Pickett s answer because in my case I needed to search deeper than one attribute level   function findWithAttr array  attr  value      if  attr indexOf       gt   0        var split   attr split           var attr1   split 0       var attr2   split 1       for var i   0  i  lt  array length  i    1          if array i  attr1  attr2      value            return i                    else       for var i   0  i  lt  array length  i    1          if array i  attr      value            return i                          You can pass  attr1 attr2  into the function

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Only way known for me is to looping through all array   var index -1  for var i 0 i lt Data length i      if Data i  name    John   index i break     or case insensitive   var index -1  for var i 0 i lt Data length i      if Data i  name toLowerCase      john   index i break     On result variable index contain index of object or -1 if not found

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var index   Data findIndex item   gt  item name     John     Which is a simplified version of   var index   Data findIndex function item   return item name     John      From mozilla org      The findIndex   method returns the index of the first element in the array that satisfies the provided testing function  Otherwise -1 is returned

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If you want to get the value of the property token then you can also try this      let data           id list  1  name   Nick   token   312312             id list  2  name   John   token   123123                let resultingToken    data   findKey data   name   John     token    where   findKey is a lodash s function

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If you re having issues with IE  you could use the map   function which is supported from 9 0 onward   var index   Data map item   gt  item name  indexOf  Nick

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Since the sort part is already answered  I m just going to propose another elegant way to get the indexOf of a property in your array  Your example is   var Data          id list 1  name  Nick  token  312312         id list 2 name  John  token  123123       You can do   var index   Data map function e    return e name     indexOf  Nick      Array prototype map is not available on IE7 or IE8  ES5 Compatibility  And here it is with ES6 and arrow syntax  which is even simpler   const index   Data map e   gt  e name  indexOf  Nick

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This might be useful  function showProps obj  objName        var result           for  var i in obj        result    objName         i           obj i      n       return result        Copied this from https   developer mozilla org en JavaScript Guide Working with Objects

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If you re fine with using ES6  Arrays now have the findIndex function  Which means you can do something like this   const index   Data findIndex item   gt  item name      John

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let indexOf   -1  let theProperty    value  let searchFor    something    theArray every function  element  index         if  element theProperty      searchFor            indexOf   index          return false            return true

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var fields     teste        Acess                Edit  true        View  false              teste1        Acess                Edit  false        View  false                  console log find fields  teste     function find fields field       for key in fields           if key    field           return true          return false      If you have one Object with multiply objects inside  if you want know if some object are include on Master object  just put find MasterObject  Object to Search    this function will return the response if exist or not  TRUE or FALSE   I hope help with this  can see the exemple on    JSFiddle

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Just go through your array and find the position   var i   0  for var item in Data        if Data item  name     John           break      i      alert i

User · Answer

Alternatively to German Attanasio Ruiz s answer  you can eliminate the 2nd loop by using Array reduce   instead of Array map     var Data           name   hypno7oad      var indexOfTarget   Data reduce function  indexOfTarget  element  currentIndex        return  element name      hypno7oad     currentIndex   indexOfTarget     -1

[javascript] How to get index of object by its property in JavaScript?

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