How to determine if Javascript array contains an object with an attribute that equals a given value

Question

I have an array like vendors          Name   Magenic       ID   ABC               Name   Microsoft       ID   DEF         and so on         How do I check this array to see if  quot Magenic quot  exists  I don t want to loop  unless I have to  I m working with potentially a couple thousand records

User · Answer

My approach to solving this problem is to use ES6 and creating a function that does the check for us. The benefit of this function is that it can be reusable through out your project to check any array of objects given the key and the value to check.

ENOUGH TALK, LET'S SEE THE CODE

Array

const ceos = [
  {
    name: "Jeff Bezos",
    company: "Amazon"
  }, 
  {
    name: "Mark Zuckerberg",
    company: "Facebook"
  }, 
  {
    name: "Tim Cook",
    company: "Apple"
  }
];

Function

const arrayIncludesInObj = (arr, key, valueToCheck) => {
  return arr.some(value => value[key] === valueToCheck);
}

Call/Usage

const found = arrayIncludesInObj(ceos, "name", "Tim Cook"); // true

const found = arrayIncludesInObj(ceos, "name", "Tim Bezos"); // false

User · Answer

You cannot without looking into the object really   You probably should change your structure a little  like  vendors         Magenic     ABC       Microsoft   DEF       Then you can just use it like a lookup-hash   vendors  Microsoft        DEF  vendors  Apple       undefined

User · Answer

Many answers here are good and pretty easy  But if your array of object is having a fixed set of value then you can use below trick   Map all the name in a object   vendors                 Name   Magenic         ID   ABC                      Name   Microsoft         ID   DEF            var dirtyObj      for var count 0 count lt vendors length count        dirtyObj vendors count  Name    true   or assign which gives you true      Now this dirtyObj you can use again and again without any loop   if dirtyObj vendor Name      console log  Hey  I am available

User · Answer

As per ECMAScript 6 specification  you can use findIndex   const magenicIndex   vendors findIndex vendor   gt  vendor Name      Magenic     magenicIndex will hold either 0  which is the index in the array  or -1 if it wasn t found

User · Answer

const check   vendors find  item   gt item Name    Magenic    console log check   Try this code  If the item or element is present then the output will show you that element  If it is not present then the output will be  undefined

User · Answer

Alternatively you can do   const find    key  needle    gt  return    vendors findIndex v   gt   v key      needle

User · Answer

Testing for array elements   JS Offers array functions which allow you to achieve this relatively easily  They are the following    Array prototype filter  Takes a callback function which is a test  the array is then iterated over with is callback and filtered according to this callback  A new filtered array is returned  Array prototype some   Takes a callback function which is a test  the array is then iterated over with is callback and if any element passes the test  the boolean true is returned  Otherwise false is returned   The specifics are best explained via an example   Example    x000D   x000D  vendors     x000D        x000D        Name   Magenic   x000D        ID   ABC  x000D          x000D        x000D        Name   Microsoft   x000D        ID   DEF  x000D          and so on goes array     x000D     x000D   x000D     filter returns a new array  we instantly check if the length  x000D     is longer than zero of this newly created array x000D  if  vendors filter company   gt  company Name      Magenic   length     x000D    console log  I contain Magenic    x000D    x000D   x000D     some would be a better option then filter since it directly returns a boolean x000D  if  vendors some company   gt  company Name      Magenic      x000D    console log  I also contain Magenic    x000D    x000D   x000D   x000D    Browser support   These 2 function are ES6 function  not all browsers might support them  To overcome this you can use a polyfill  Here is the polyfill for Array prototype some  from MDN     x000D   x000D  if   Array prototype some    x000D    Array prototype some   function fun  thisArg    x000D       use strict   x000D   x000D      if  this    null    x000D        throw new TypeError  Array prototype some called on null or undefined    x000D        x000D   x000D      if  typeof fun      function     x000D        throw new TypeError    x000D        x000D   x000D      var t   Object this   x000D      var len   t length  gt  gt  gt  0  x000D   x000D      for  var i   0  i  lt  len  i      x000D        if  i in t  amp  amp  fun call thisArg  t i   i  t     x000D          return true  x000D          x000D        x000D   x000D      return false  x000D       x000D    x000D   x000D   x000D

User · Answer

No need to reinvent the wheel loop  at least not explicitly  using arrow functions  modern browsers only    if  vendors filter e   gt  e Name      Magenic   length  gt  0         vendors contains the element we re looking for        or  better yet   if  vendors some e   gt  e Name      Magenic           vendors contains the element we re looking for        EDIT  If you need compatibility with lousy browsers then your best bet is   if  vendors filter function e    return e Name      Magenic      length  gt  0         vendors contains the element we re looking for

User · Answer

Correct me if i m wrong   i could have used forEach method like this   var found false  vendors forEach function item      if item name      name           found true              Nowadays i m used to it  because of it simplicity and self explanatory word  Thank you

User · Answer

As the OP has asked the question if the key exists or not    A more elegant solution that will return boolean using ES6 reduce function can be  const magenicVendorExists    vendors reduce  accumulator  vendor    gt   accumulator  vendor Name      Magenic    false     Note   The initial parameter of reduce is a false and if the array has the key it will return true   Hope it helps for better and cleaner code implementation

User · Answer

const a     one 2   two 2   two 4   const b   a filter val   gt   two  in val  length  if  b

User · Answer

var without2    arr  args    gt  arr filter v   gt  v id     args id    Example   without2   id 1   id 1   id 2    id 2     Result  without2   id 1   id 1   id 2    id 2

User · Answer

Unless you want to restructure it like this   vendors         Magenic          Name   Magenic         ID   ABC              Microsoft          Name   Microsoft         ID   DEF        and so on          to which you can do if vendors Magnetic   You will have to loop

User · Answer

I would rather go with regex   If your code is as follows   vendors                 Name   Magenic         ID   ABC                      Name   Microsoft         ID   DEF             I would recommend    Name   Magenic   test JSON stringify vendors

User · Answer

You can use lodash  If lodash library is too heavy for your application consider chunking out unnecessary function not used   let newArray   filter  this props ArrayOne  function item                        return find  this props ArrayTwo    speciesId   item speciesId                          This is just one way to do this  Another one can be   var newArray              filter ArrayOne  function item                            return AllSpecies forEach function cItem                               if  cItem speciesId    item speciesId                               newArray push item                                                                                     console log arr    The above example can also be rewritten without using any libraries like   var newArray       ArrayOne filter function item                    return ArrayTwo forEach function cItem                       if  cItem speciesId    item speciesId                       newArray push item                                                           console log arr     Hope my answer helps

User · Answer

No loop necessary  Three methods that come to mind   Array prototype some    This is the most exact answer for your question  i e   check if something exists   implying a bool result  This will be true if there are any  Magenic  objects  false otherwise   let hasMagenicVendor   vendors some  vendor   gt  vendor  Name        Magenic      Array prototype filter    This will return an array of all  Magenic  objects  even if there is only one  will return a one-element array    let magenicVendors   vendors filter  vendor   gt  vendor  Name        Magenic      If you try to coerce this to a boolean  it will not work  as an empty array  no  Magenic  objects  is still truthy  So just use magenicVendors length in your conditional   Array prototype find    This will return the first  Magenic  object  or undefined if there aren t any    let magenicVendor   vendors find  vendor   gt  vendor  Name        Magenic       This coerces to a boolean okay  any object is truthy  undefined is falsy      Note  I m using vendor  Name   instead of vendor Name because of the weird casing of the property names   Note 2  No reason to use loose equality      instead of strict equality       when checking the name

User · Answer

You can use includes from the Ramda library  i e  R includes   name   Fred        name   Fred           gt  true  Source  https   ramdajs com docs  includes

User · Answer

To compare one object to another  I combine a for in loop  used to loop through objects  and some    You do not have to worry about an array going out of bounds etc  so that saves some code  Documentation on  some can be found here  var productList     id   text3     id   text2     id   text4   product   Shampoo        Example of selected products var theDatabaseList     id   text1     id   text2    id   text3    id  text4   product   shampoo         var  objectsFound        for let objectNumber in productList       var currentId   productList objectNumber  id         if  theDatabaseList some obj   gt  obj id     currentId                Do what you need to do with the matching value here         objectsFound push currentId           console log objectsFound     An alternative way I compare one object to another is to use a nested for loop with Object keys   length to get the amount of objects in the array  Code below   var productList     id   text3     id   text2     id   text4   product   Shampoo        Example of selected products var theDatabaseList     id   text1     id   text2    id   text3    id  text4   product   shampoo         var objectsFound        for var i   0  i  lt  Object keys productList  length  i             for var j   0  j  lt  Object keys theDatabaseList  length  j             if productList i  id     theDatabaseList j  id               objectsFound push productList i  id                            console log objectsFound     To answer your exact question  if are just searching for a value in an object  you can use a single for in loop   var vendors                 Name   Magenic         ID   ABC                      Name   Microsoft         ID   DEF             for var ojectNumbers in vendors       if vendors ojectNumbers  Name      Magenic            console log  object contains Magenic

User · Answer

if you re using jquery you can take advantage of grep to create array with all matching objects   var results     grep vendors  function  e        return e Name     Magenic         and then use the results array   for  var i 0  l results length  i lt l  i          console log results i  ID

User · Answer

The accepted answer still works but now we have an ECMAScript 6 native method  Array find  1  to achieve the same effect    Quoting MDN      The find   method returns the value of the first element in the array   that satisfies the provided testing function  Otherwise undefined is   returned    var arr        var item       id   21     step   step2     label   Banana     price   19       arr push item      note   data is the actual object that matched search criteria    or undefined if nothing matched    var data   arr find  function  ele          return ele id      21         if  data      console log   found      console log data      This is entire object i e   item  not boolean     See my jsfiddle link There is a polyfill for IE provided by mozilla

User · Answer

You can try this its work for me   const     require  lodash     var arr             name   Jack       id  1              name   Gabriel       id  2              name   John       id  3        function findValue arr value      return   filter arr  function  object        return object  name   toLowerCase   indexOf value toLowerCase     gt   0           console log findValue arr  jack          name   Jack   id  1

User · Answer

Here s the way I d do it  const found   vendors some item   gt  item Name      Magenic      array some   method checks if there is at least one value in an array that matches criteria and returns a boolean   From here on you can go with   if  found       do something   else      do something else

User · Answer

2018 edit  This answer is from 2011  before browsers had widely supported array filtering methods and arrow functions  Have a look at CAFxX s answer   There is no  magic  way to check for something in an array without a loop  Even if you use some function  the function itself will use a loop  What you can do is break out of the loop as soon as you find what you re looking for to minimize computational time   var found   false  for var i   0  i  lt  vendors length  i          if  vendors i  Name     Magenic             found   true          break

User · Answer

May be too late  but javascript array has two methods some and every method that returns a boolean and can help you achieve this   I think some would be most appropriate for what you intend to achieve   vendors some  vendor   gt  vendor  Name        Magenic      Some validates that any of the objects in the array satisfies the given condition   vendors every  vendor   gt  vendor  Name        Magenic      Every validates that all the objects in the array satisfies the given condition

User · Answer

You have to loop  there is no way around it   function seekVendor vendors  name      for  var i 0  l vendors length  i lt l  i          if  typeof vendors i      object   amp  amp  vendors i  Name     name          return vendors i                 Of course you could use a library like linq js to make this more pleasing   Enumerable From vendors  Where    Name     Magenic    First       see jsFiddle for a demo   I doubt that linq js will be faster than a straight-forward loop  but it certainly is more flexible when things get a little more complicated

User · Answer

x000D   x000D  const VENDORS      Name   Magenic   ID   ABC       Name   Microsoft   ID   DEF       console log   some VENDORS    Name    Magenic      x000D   lt script src  https   cdn jsdelivr net npm lodash 4 17 20 lodash min js  gt  lt  script gt  x000D   x000D   x000D

[javascript] How to determine if Javascript array contains an object with an attribute that equals a given value?

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