How to get the first element of an array

Question

How do you get the first element from an array like this   var ary     first    second    third    fourth    fifth      I tried this   alert   ary  first       But it would return  object Object   So I need to get the first element from the array which should be the element  first

User · Answer

You can do it by lodash   head so easily    x000D   x000D  var arr     first    second    third    fourth    fifth    x000D  console log   head arr    x000D   lt script src  https   cdnjs cloudflare com ajax libs lodash js 4 17 11 lodash min js  gt  lt  script gt  x000D   x000D   x000D

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var ary     first    second    third    fourth    fifth     console log Object keys ary  0      Make any Object array  req   then simply do Object keys req  0  to pick the first key in the Object array

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Some of ways below for different circumstances    In most normal cases  the simplest way to access the first element is by   yourArray 0    but this requires you to check if  0  actually exists    There are real world cases where you don t care about the original array  and don t want to check if index exists  you want just to get the first element or undefined inline    In this case  you can use shift   method to get the first element  but be cautious that this method modifies the original array  removes the first item and returns it   Therefore the length of an array is reduced by one   This method can be used in inline cases where you just need to get the first element  but you dont care about the original array    yourArray shift     The important thing to know is that the two above are only an option if your array starts with a  0  index   There are cases where the first element has been deleted  example with  delete yourArray 0  leaving your array with  holes   Now the element at  0  is simply undefined  but you want to get the first  existing  element  I have seen many real world cases of this    So  assuming we have no knowledge of the array and the first key  or we know there are holes   we can still get the first element   You can use find   to get the first element    The advantage of find   is its efficiency as it exits the loop when the first value satisfying the condition is reached  more about this below    You can customize the condition to exclude null or other empty values too   var firstItem   yourArray find x  gt x   undefined     I d also like to include filter   here as an option to first  fix  the array in the copy and then get the first element while keeping the the original array intact  unmodified     Another reason to include filter   here is that it existed before find   and many programmers have already been using it  it is ES5 against find   being ES6     var firstItem   yourArray filter x   gt  typeof x   undefined  shift      Warning that filter   is not really an efficient way  filter   runs through all elements  and creates another array  It is fine to use on small arrays as performance impact would be marginal  closer to using forEach  for example     I see some people suggest using for   in loop to get the first element  but I would recommend against this method for   in should not be used to iterate over an Array where the index order is important because it doesn t guarantee the order although you can argue browsers mostly respect the order By the way  forEach doesn t solve the issue as many suggest because you cant break it and it will run through all elements  You would be better off using a simple for loop and by checking key value  Both find   and filter   guarantee the order of elements  so are safe to use as above

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If you want to preserve the readibility you could always add a first function to the Array protoype   Array prototype first   function          return this 0        A then you could easily retrieve the first element    1  2  3  first     gt  1

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NicoLwk You should remove elements with splice  that will shift your array back  So     var a   a   b   c    a splice 0 1   for var i in a  console log i     a i

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Use this to split character in javascript   var str    boy  girl  dog  cat   var arr   str split       var fst   arr splice 0 1  join      var rest   arr join

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Find the first element in an array using a filter   In typescript   function first lt T gt  arr  T    filter   v  T    gt  boolean   T       let result  T      return arr some v   gt    result   v  return filter v        result   undefined      In plain javascript   function first arr  filter        var result      return arr some function  v    result   v  return filter v        result   undefined      And similarly  indexOf   In typescript   function indexOf lt T gt  arr  T    filter   v  T    gt  boolean   number       let result  number      return arr some  v  i    gt    result   i  return filter v        result   undefined      In plain javascript   function indexOf arr  filter        var result      return arr some function  v  i    result   i  return filter v        result   undefined

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You can just use find     let first   array find Boolean     Or if you want the first element even if it is falsy   let first   array find e   gt  true       Going the extra mile   If you care about readability but don t want to rely on numeric incidences you could add a first  -function to Array protoype by defining it with Object  define Property   which mitigates the pitfalls of modifying the built-in Array object prototype directly  explained here     Performance is pretty good  find   stops after the first element  but it isn t perfect or universally accessible  ES6 only   For more background read  Selays answer   Object defineProperty Array prototype   first       value         return this find e   gt  true          or this find Boolean            Then to retrieve the first element you can do   let array     a    b    c    array first      gt   a    Snippet to see it in action    x000D   x000D  Object defineProperty Array prototype   first     x000D    value     x000D      return this find Boolean   x000D      x000D      x000D   x000D  console log    a    b    c   first      x000D   x000D   x000D

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Why not account for times your array might be empty   var ary     first    second    third    fourth    fifth    first    array    gt  array length   array 0     no items   first ary     output  first  var ary       first ary     output  no items

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The previous examples work well when the array index begins at zero  thomax s answer did not rely on the index starting at zero  but relied on Array prototype find to which I did not have access  The following solution using jQuery   each worked well in my case   let haystack    100   first   150   second        found   null     each haystack  function  index  value         found   value      Save the first array element for later      return false      Immediately stop the   each loop after the first array element       console log found      Prints  first

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like this  alert ary 0

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ES6 easy   let a      a 7     A  a 10     B   let firstValue   a find v   gt  v  let firstIndex   a findIndex v   gt  v

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You could also use  get 0    alert   ary  first   get 0      To get the first element of the array

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Element of index 0 may not exist if the first element has been deleted    x000D   x000D  let a     a    b    c    x000D  delete a 0   x000D   x000D  for  let i in a    x000D    console log i         a i    x000D    x000D   x000D   x000D    Better way to get the first element without jQuery    x000D   x000D  function first p    x000D    for  let i in p  return p i   x000D    x000D   x000D  console log  first   a    b    c       x000D   x000D   x000D

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You can use the combination of reverse then pop  The idea is to reverse the array then pop which will get you the last item in that array   Be careful as this will modify the original array    x000D   x000D  var fruits     Banana    Orange    Lemon    Apple    Mango    x000D  var first   fruits reverse   pop    x000D     x000D  console log  First element -- gt    first   x000D  console log  Original array -- gt    fruits   x000D   x000D   x000D

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Method that works with arrays  and it works with objects too  beware  objects don t have a guaranteed order     I prefer this method the most  because original array is not modified      In case of array var arr       arr 3     first   arr 7     last   var firstElement  for var i in arr       firstElement   arr i       break    console log firstElement        first      In case of object var obj         first   first       last   last       var firstElement   for var i in obj       firstElement   obj i       break     console log firstElement     First

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Try alert ary 0

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I know that people which come from other languages to JavaScript  looking for something like head   or first   to get the first element of an array  but how you can do that   Imagine you have the array below   const arr    1  2  3  4  5     In JavaScript  you can simply do   const first   arr 0     or a neater  newer way is   const  first    arr    But you can also simply write a function like     function first arr       if  Array isArray arr   return     return arr 0       If using underscore  there are list of functions doing the same thing you looking for     first     head    take

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Only in case you are using underscore js  http   underscorejs org   you can do     first your array

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array find e   gt    e       return the first element    since  find  return the first element that matches the filter  amp  amp    e match any element   Note  This works only when the first element is not a  Falsy    null  false  NaN      0  undefined

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Using ES6 destructuring  let  first     1 2 3     Which is the same as  let first    1 2 3  0

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When there are multiple matches  JQuery s  first   is used for fetching the first DOM element that matched the css selector given to jquery    You don t need jQuery to manipulate javascript arrays

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thomax  s answer is pretty good  but will fail if the first element in the array is false or false-y  0  empty string  etc    Better to just return true for anything other than undefined   const arr       arr 1        arr 2     foo    const first   arr find  v    gt    return  typeof v      undefined        console log first

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Why are you jQuery-ifying a vanilla JavaScript array  Use standard JavaScript  var ary     first    second    third    fourth    fifth    alert ary 0     https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Array Also   Source  courtesy of bobince

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Just use ary slice 0 1  pop     In   x000D   x000D  var ary     first    second    third    fourth    fifth    x000D   x000D  console log  1     ary slice 0 1  pop     x000D  console log  2     ary slice 0 2  pop     x000D  console log  3     ary slice 0 3  pop     x000D  console log  4     ary slice 0 4  pop     x000D  console log  5     ary slice 0 5  pop     x000D  console log  Last   ary slice -1  pop     x000D   x000D   x000D    array slice START END  pop

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In ES2015 and above  using array destructuring    x000D   x000D  const arr    42  555  666  777  x000D  const  first    arr x000D  console log first  x000D   x000D   x000D

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ES6 Spread operator    shift   solution Using myArray shift   you can get the 1st element of the array  but  shift   will modify the original array  so to avoid this  first you can create a copy of the array with     myArray  and then apply the  shift   to this copy   x000D   x000D  var myArray     first    second    third    fourth    fifth     var first       myArray  shift             console log first   x000D   x000D   x000D

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If your array is not guaranteed to be populated from index zero  you can use Array prototype find     var elements      elements 1     foo  elements 2     bar   var first   function element    return   element       var gotcha   elements find first   console log a 0      undefined console log gotcha      foo

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x000D   x000D  var ary     first    second    third    fourth    fifth    x000D  alert Object values ary  0    x000D   x000D   x000D

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Using ES6  let arr    22 1 4 55 7 8 9 3 2 4    let  0   first   arr length - 1    last    arr  console log first  last    or let  0   first  length   l   l - 1    last     22 1 4 55 7 8 9 3 2 4   console log first  last

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If you re chaining a view functions to the array e g   array map i   gt  i 1  filter i   gt  i  gt  3   And want the first element after these functions you can simply add a  shift   it doesn t modify the original array  its a nicer way then array map i   gt  i 1  filter   gt  i  gt  3  0   If you want the first element of an array without modifying the original you can use array 0  or array map n  gt n  shift    without the map you will modify the original  In this case btw i would suggest the    0  version

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Declare a prototype to get first array element as   Array prototype first   function         return this 0        Then use it as   var array    0  1  2  3   var first   array first    var  first    0  1  2  3  first      Or simply     first   array 0

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Another one for those only concerned with truthy elements  ary find Boolean

[javascript] How to get the first element of an array?

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