Get JavaScript object from array of objects by value of property

Question

Let s say I have an array of four objects   var jsObjects         a  1  b  2        a  3  b  4        a  5  b  6        a  7  b  8       Is there a way that I can get the third object   a  5  b  6   by the value of the property b for example without a for   in loop

User · Answer

If you are looking for a single result  rather than an array  may I suggest reduce    Here is a solution in plain  ole javascript that returns a matching object if one exists  or null if not   var result   arr reduce function prev  curr    return  curr b     6    curr   prev     null

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OK  there are few ways to do that  but let s start with the simplest one and latest approach to do this  this function is called find     Just be careful when you using find to as even IE11 dosn t support it  so it needs to be transpiled     so you have this object as you said   var jsObjects         a  1  b  2        a  3  b  4        a  5  b  6        a  7  b  8       and you can write a function and get it like this   function filterValue obj  key  value      return obj find function v   return v key      value        and use the function like this   filterValue jsObjects   b   6      a  5  b  6    Also in ES6 for even shortened version   const filterValue    obj  key  value   gt  obj find v   gt  v key      value     This method only return the first value which match     for better result and browser support  you can use filter   const filterValue    obj  key  value   gt  obj filter v   gt  v key      value     and we will return   a  5  b  6       This method will return an array instead     You simpley use for loop as well  create a function like this   function filteredArray arr  key  value      const newArray         for i 0  l arr length  i lt l  i          if arr i  key      value          newArray push arr i               return newArray      and call it like this   filteredArray jsObjects   b   6       a  5  b  6

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How about using   find collection   predicate   identity    fromIndex 0   of lo-dash to get object from array of objects by object property value  You could do something like this    var o     find jsObjects    b   6      Arguments    collection  Array Object   The collection to inspect   predicate   identity   Function   The function invoked per iteration   fromIndex 0   number   The index to search from    Returns       Returns the matched element  in your case   a  5  b  6    else undefined    In terms of performance    find   is faster as it only pulls the first object with property   b   6   on the other hand  if suppose your array contains multiple objects with matching set of properties  key value   then you should consider using   filter   method  So in your case  as your array has a single object with this property  I would use   find

User · Answer

I don t know why you are against a for loop  presumably you meant a for loop  not specifically for  in   they are fast and easy to read  Anyhow  here s some options  For loop  function getByValue arr  value       for  var i 0  iLen arr length  i lt iLen  i           if  arr i  b    value  return arr i           filter function getByValue2 arr  value       var result    arr filter function o  return o b    value         return result  result 0    null     or undefined      forEach function getByValue3 arr  value       var result          arr forEach function o  if  o b    value  result push o          return result  result 0    null     or undefined     If  on the other hand you really did mean for  in and want to find an object with any property with a value of 6  then you must use for  in unless you pass the names to check  Example function getByValue4 arr  value      var o     for  var i 0  iLen arr length  i lt iLen  i          o   arr i        for  var p in o          if  o hasOwnProperty p   amp  amp  o p     value            return o

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Try Array filter method for filter the array of objects with property   var jsObjects         a  1  b  2        a  3  b  4        a  5  b  6        a  7  b  8       using array filter method   var filterObj   jsObjects filter function e      return e b    6        using for in loop    for  var i in jsObjects      if  jsObjects i  b    6        console log jsObjects i        a  5  b  6          Working fiddle   https   jsfiddle net uq9n9g77

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It looks like in the ECMAScript 6 proposal there are the Array methods find   and findIndex    MDN also offers polyfills which you can include to get the functionality of these across all browsers   find     function isPrime element  index  array        var start   2      while  start  lt   Math sqrt element             if  element   start    lt  1  return false            return  element  gt  1      console log   4  6  8  12  find isPrime        undefined  not found console log   4  5  8  12  find isPrime        5   findIndex     function isPrime element  index  array        var start   2      while  start  lt   Math sqrt element             if  element   start    lt  1  return false            return  element  gt  1      console log   4  6  8  12  findIndex isPrime        -1  not found console log   4  6  7  12  findIndex isPrime        2

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You can use it with the arrow function as well like as below    var demoArray         name   apples   quantity  2       name   bananas   quantity  0       name   cherries   quantity  5      var result   demoArray filter  obj   gt  obj name      apples   0   console log result       name   apples   quantity  2

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To get first object from array of objects by a specific property value    x000D   x000D  function getObjectFromObjectsArrayByPropertyValue objectsArray  propertyName  propertyValue    x000D    return objectsArray find function  objectsArrayElement    x000D      return objectsArrayElement propertyName     propertyValue  x000D        x000D    x000D   x000D  function findObject      x000D    var arrayOfObjectsString   document getElementById  arrayOfObjects   value  x000D        arrayOfObjects  x000D        propertyName   document getElementById  propertyName   value  x000D        propertyValue   document getElementById  propertyValue   value  x000D        preview   document getElementById  preview    x000D        searchingObject  x000D     x000D    arrayOfObjects   JSON parse arrayOfObjectsString   x000D     x000D    console debug arrayOfObjects   x000D     x000D    if arrayOfObjects  amp  amp  propertyName  amp  amp  propertyValue    x000D      searchingObject   getObjectFromObjectsArrayByPropertyValue arrayOfObjects  propertyName  propertyValue   x000D      if searchingObject    x000D        preview innerHTML   JSON stringify searchingObject  false  2   x000D        else   x000D        preview innerHTML    there is no object with property     propertyName           propertyValue     in your array of objects   x000D        x000D      x000D    x000D  pre   x000D    padding  5px  x000D    border-radius  4px  x000D    background   f3f2f2  x000D    x000D   x000D  textarea  button   x000D    width  100  x000D    x000D   lt fieldset gt  x000D     lt legend gt Input Data  lt  legend gt  x000D     lt label gt Put here your array of objects lt  label gt  x000D     lt textarea rows  7  id  arrayOfObjects  gt  x000D      x000D        a   1   b   2   x000D        a   3   b   4   x000D        a   5   b   6   x000D        a   7   b   8   c   157  x000D      x000D     lt  textarea gt  x000D   x000D     lt hr gt  x000D   x000D     lt label gt property name   lt  label gt   lt input type  text  id  propertyName   value  b   gt  x000D     lt label gt property value   lt  label gt   lt input type  text  id  propertyValue  value 6   gt  x000D        x000D   lt  fieldset gt  x000D   lt hr gt  x000D   lt button onclick  findObject    gt find object in array  lt  button gt  x000D   lt hr gt  x000D   lt fieldset gt  x000D     lt legend gt Searching Result  lt  legend gt  x000D     lt pre id  preview  gt click find lt  pre gt  x000D   lt  fieldset gt  x000D   x000D   x000D

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Using find with bind to pass specific key values to a callback function       function byValue o            return o a     this a  amp  amp  o b     this b                var result   jsObjects find byValue bind   a  5  b  6

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See this documentation Array prototype find   Example  var inventory          name   apples   quantity  2        name   bananas   quantity  0        name   cherries   quantity  5      function findCherries fruit         return fruit name      cherries      console log inventory find findCherries          name   cherries   quantity  5

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Made the best fastest part of this answer more re-usable  amp  clear   function getElByPropVal myArray  prop  val       for  var i   0  length   myArray length  i  lt  length  i              if  myArray i  prop     val               return myArray i

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var jsObjects     a  1  b  2    a  3  b  4    a  5  b  6    a  7  b  8      to access the third object  use  jsObjects 2   to access the third object b value  use  jsObjects 2  b

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jsObjects find x   gt  x b     6    From MDN      The find   method returns a value in the array  if an element in the array satisfies the provided testing function  Otherwise undefined is returned      Side note  methods like find   and arrow functions are not supported by older browsers  like IE   so if you want to support these browsers  you should transpile your code using Babel

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If I understand correctly  you want to find the object in the array whose b property is 6   var found  jsObjects some function  obj      if  obj b     6        found   obj      return true            Or if you were using underscore   var found     select jsObjects  function  obj      return obj b     6

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var result   jsObjects filter x  gt  x b     6     will be better  using return in filter sometimes you can t get result  I dunno why

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Filter array of objects  which property matches value  returns array   var result   jsObjects filter obj   gt      return obj b     6      See the MDN Docs on Array prototype filter     x000D   x000D  const jsObjects     x000D     a  1  b  2    x000D     a  3  b  4    x000D     a  5  b  6    x000D     a  7  b  8  x000D    x000D   x000D  let result   jsObjects filter obj   gt    x000D    return obj b     6 x000D     x000D   x000D  console log result  x000D   x000D   x000D    Find the value of the first element object in the array  otherwise undefined is returned   var result   jsObjects find obj   gt      return obj b     6      See the MDN Docs on Array prototype find     x000D   x000D  const jsObjects     x000D     a  1  b  2    x000D     a  3  b  4    x000D     a  5  b  6    x000D     a  7  b  8  x000D    x000D   x000D  let result   jsObjects find obj   gt    x000D    return obj b     6 x000D     x000D   x000D  console log result  x000D   x000D   x000D

User · Answer

Using underscore js   var foundObject     findWhere jsObjects   b  6

[javascript] Get JavaScript object from array of objects by value of property

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