Array push if does not exist

Question

How can I push into an array if neither values exist  Here is my array           name   tom   text   tasty           name   tom   text   tasty           name   tom   text   tasty           name   tom   text   tasty           name   tom   text   tasty        If I tried to push again into the array with either name   tom  or text   tasty   I don t want anything to happen    but if neither of those are there then I want it to  push    How can I do this

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Use a js library like underscore js for these reasons exactly  Use  union  Computes the union of the passed-in arrays  the list of unique items  in order  that are present in one or more of the arrays     union  1  2  3    101  2  1  10    2  1      gt   1  2  3  101  10

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You can use the findIndex method with a callback function and its  this  parameter   Note  old browsers don t know findIndex but a polyfill is available   Sample code  take care that in the original question  a new object is pushed only if neither of its data is in previoulsy pushed objects    var a   name  tom   text  tasty     b  var magic function e        return   e name    this name      e text    this text        b  name  tom   text  tasty    if  a findIndex magic b     -1      a push b      nothing done b  name  tom   text  ugly    if  a findIndex magic b     -1      a push b      nothing done b  name  bob   text  tasty    if  a findIndex magic b     -1      a push b      nothing done b  name  bob   text  ugly    if  a findIndex magic b     -1      a push b      b is pushed into a

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For an array of strings  but not an array of objects   you can check if an item exists by calling  indexOf   and if it doesn t then just push the item into the array    x000D   x000D  var newItem    NEW ITEM TO ARRAY   x000D  var array     OLD ITEM 1    OLD ITEM 2    x000D   x000D  array indexOf newItem      -1   array push newItem    console log  This item already exists    x000D   x000D  console log array  x000D   x000D   x000D

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a is the array of objects you have  a findIndex x   gt  x property   WhateverPropertyYouWantToMatch    lt 0    a push objectYouWantToPush    console log  response if object exists

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It is quite easy to do using the Array findIndex function  which takes a function as an argument  var arrayObj     name  quot bull quot   text   quot sour quot          name   quot tom quot   text   quot tasty quot           name   quot tom quot   text   quot tasty quot      var index   arrayObj findIndex x   gt  x name   quot bob quot        here you can check specific property for an object whether it exist in your array or not  index     -1   arrayObj push  your object     console log  quot object already exists quot

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I know this is a very old question  but if you re using ES6 you can use a very small version    1 2 3  filter f   gt  f     3  concat  3     Very easy  at first add a filter which removes the item - if it already exists  and then add it via a concat   Here is a more realistic example   const myArray     hello    world   const newArrayItem  myArray filter f   gt  f     newArrayItem  concat  newArrayItem     If you re array contains objects you could adapt the filter function like this   someArray filter f   gt  f some s   gt  s id     myId   concat    id  myId

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Easy code  if  indexOf  returns  -1  it means that element is not inside the array then the condition      -1  retrieve true false   The   amp  amp   operator means  and   so if the first condition is true we push it to the array   array indexOf newItem      -1  amp  amp  array push newItem

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In case you need something simple without wanting to extend the Array prototype      Example array var array     id  1    id  2    id  3     function pushIfNew obj      for  var i   0  i  lt  array length  i          if  array i  id     obj id       modify whatever property you need       return              array push obj

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This is working func for an objects comparison  In some cases you might have lot of fields to compare  Simply loop the array and call this function with a existing items and new item    var objectsEqual   function  object1  object2            if  object1     object2              return false          var result   true          var arrayObj1     keys object1           var currentKey               for  var i   0  i  lt  arrayObj1 length  i                  currentKey   arrayObj1 i               if  object1 currentKey      null  amp  amp  object2 currentKey      null                  if     has object2  currentKey                            isEqual object1 currentKey  toUpperCase    object2 currentKey  toUpperCase                         return false                    return result

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http   api jquery com jQuery unique   var cleanArray     unique clutteredArray     you might be interested in makeArray too  The previous example is best in saying that check if it exists before pushing  I see in hindsight it also states you can declare it as part of the prototype  I guess that s aka Class Extension   so no big enhancement below   Except I m not sure if indexOf is a faster route then inArray  probably   Array prototype pushUnique   function  item       if this indexOf item     -1          if jQuery inArray item  this     -1            this push item           return true            return false

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In case anyone has less complicated requirements  here is my adaptation of the answer for a simple string array   Array prototype pushIfNotExist   function val        if  typeof val      undefined     val          return        val     trim val       if    inArray val  this     -1            this push val              Update  Replaced indexOf and trim with jQuery alternatives for IE8 compatability

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You can check the array using foreach and then pop the item if it exists otherwise add new item     sample newItemValue  amp submitFields are key value pairs   gt    submitFields existing array  gt       angular forEach submitFields  function item     gt                    index      newItemValue new key value to check  gt                      if  newItemValue    item value     gt                        submitFields splice index-1 1    gt                            gt                                             submitFields push   field  field  value  value

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Not sure about speed  but stringification   indexOf is a simple approach  Start with turning your array into a string   let strMyArray   JSON stringify myArray     Then for a series of attribute-value pairs you can use   if  strMyArray indexOf   name   tom        -1  amp  amp  strMyArray indexOf   text   tasty        -1       myArray push   name   tom   text   tasty          Finding a whole object is simpler   if  strMyArray indexOf JSON stringify objAddMe      -1        myArray push objAddMe

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Push dynamically       var a        name  bull   text   sour       name   tom   text   tasty        name   Jerry   text   tasty       function addItem item      var index   a findIndex x   gt  x name    item name    if  index     -1        a push item      else       console log  object already exists          var item    name  bull   text   sour    addItem item     In simple method  var item    name  bull   text   sour    a findIndex x   gt  x name    item name     -1   a push item    console log  object already exists     If the array contains only primitive types  simple array  var b    1  7  8  4  3   var newItem   6  b indexOf newItem      -1  amp  amp  b push newItem

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Here you have a way to do it in one line for two arrays   const startArray    1 2 3 4  const newArray    4 5 6   const result       startArray     newArray filter a   gt   startArray includes a     console log result     Result   1 2 3 4 5 6

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Removing duplicates after pushing If you already have an array containing duplicates  transform the array of objects into an array of strings  and then use the Set   function to eliminate duplicates     Declaring an array of objects containing duplicate objects let arrayOfObjects     name   quot tom quot   text   quot tasty quot     name   quot tom quot   text   quot tasty quot         Transforming array of objects into array of strings let arrayOfStrings   arrayOfObjects map obj   gt  JSON stringify obj        Creating a new set  Set   returns unique values by definition let uniqueSet   new Set arrayOfStrings       Transforming set into array and reversing strings to objects let uniqueArrayOfObjects       uniqueSet  map elem   gt  JSON parse elem     console log uniqueArrayOfObjects        name   quot tom quot   text   quot tasty quot     Checking before pushing If you don t have duplicates so far and you want to check for duplicates before pushing a new element     Declaring an array of objects without duplicates let arrayOfObjects     name   quot tom quot   text   quot tasty quot         Transforming array of objects into array of strings let arrayOfStrings   arrayOfObjects map obj   gt  JSON stringify obj        Declaring new element as an example let newElem    name   quot tom quot   text   quot tasty quot        Stringifying new element let newElemString   JSON stringify newElem       At this point  check if the string is duplicated and add it to array  arrayOfStrings includes newElemString   amp  amp  arrayOfObjects push newElem    console log arrayOfObjects        name   quot tom quot   text   quot tasty quot

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I used map and reduce to do this in the case where you wish to search by the a specific property of an object  useful as doing direct object equality will often fail   var newItem     unique id   123   var searchList      unique id    123     unique id    456     hasDuplicate   searchList     map function e  return e unique id   newItem unique id       reduce function pre  cur   return pre    cur     if  hasDuplicate       searchList push newItem     else      console log  Duplicate Item

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My choice was to use  includes   extending the Array prototype as  Darrin Dimitrov suggested  Array prototype pushIfNotIncluded   function  element        if   this includes element           array push element            Just remembering that includes comes from es6 and does not work on IE  https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Array includes

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I would suggest you use a Set   Sets only allow unique entries  which automatically solves your problem    Sets can be declared like so   const baz   new Set   Foo   Bar

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You can use jQuery grep and push if no results  http   api jquery com jQuery grep   It s basically the same solution as in the  extending the prototype  solution  but without extending  or polluting  the prototype

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You could extend the Array prototype with a custom method      check if an element exists in array using a comparer function    comparer   function currentElement  Array prototype inArray   function comparer         for var i 0  i  lt  this length  i               if comparer this i    return true             return false           adds an element to the array if it does not already exist using a comparer     function Array prototype pushIfNotExist   function element  comparer         if   this inArray comparer             this push element              var array      name   tom   text   tasty      var element     name   tom   text   tasty     array pushIfNotExist element  function e         return e name     element name  amp  amp  e text     element text

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someArray     a   a1 value   b   c   quot c1 value quot                  a   a2 value   b   c   quot c2 value quot    newObject    a   a2 value   b   c   quot c2 value quot       New object which needs check for duplicity  let isExists   checkForExists newObject        return someArray some function el            return el a     newObject a  amp  amp  el b c     newObject b c               write your logic here     if isExists is true then already object in an array else you can add

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Like this   var item    Hello World   var array       if  array indexOf item      -1  array push item     With object  var item    name   tom   text   tasty   var array        if   array find o   gt  o name      tom   amp  amp  o text      tasty        array push item

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Short example   if  typeof arr key        undefined       arr push key

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I guess i am too late to answer here however this is what i finally came up with for a mail manager i wrote  Works that s all i need    x000D   x000D  window ListManager       x000D      add   click function    x000D    Your Functionality x000D    let data  Math floor Math random     5    1  x000D     x000D    if  window ListManager includes data    x000D        console log  data exists in list   x000D     else  x000D         window ListManager push data   x000D      x000D     x000D     x000D        result   text window ListManager   x000D      x000D   lt script src  https   cdnjs cloudflare com ajax libs jquery 3 3 1 jquery min js  gt  lt  script gt  x000D   lt h1 gt Unique List lt  h1 gt  x000D   x000D   lt p id  result  gt  lt  p gt  x000D   lt button id  add  gt Add to List lt  button gt  x000D   x000D   x000D

[javascript] Array.push() if does not exist?

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