How can I clone a JavaScript object except for one key

Question

I have a flat JS object    a  1  b  2  c  3       z 26    I want to clone the object except for one element    a  1  c  3       z 26    What s the easiest way to do this  preferring to use es6 7 if possible

User · Answer

How about this   let clone   Object assign     value   delete clone unwantedKey

User · Answer

If you re dealing with a huge variable  you don t want to copy it and then delete it  as this would be inefficient   A simple for-loop with a hasOwnProperty check should work  and it is much more adaptable to future needs    for var key in someObject            if someObject hasOwnProperty key   amp  amp  key     undesiredkey                     copyOfObject key    someObject key

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Maybe something like this   var copy   Object assign      a  1  b  2  c  3   delete copy c    Is this good enough  Or can t c actually get copied

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I had an object that I wanted to remove after utilizing its method   This is what worked for me      Sample data    let items             name   John       doc          set  async  item    gt        sets docs on remote server                    name   Mary       doc          set  async  item    gt        sets docs on remote server                    name   Jack       doc          set  async  item    gt        sets docs on remote server                    mapping to promises    const promises   items map   doc     item     gt  doc set item        utilized doc and utilized  rest  of the items       Good Luck

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Lodash omit  let source      a  1  b  2  c  3       z 26  let copySansProperty     omit source   b        a  1  c  3       z 26

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I have one object named  options with some keys   let options                    userDn   somePropertyValue           username   someValue           userSearchBase   someValue           usernameAttribute   uid           userPassword   someValue         I want to log all object excelp userPassword Property because Im testing something  I am using this code  console log Object keys options  map x   gt  x           x      quot userPassword quot     ---    options x       If you want to make it dynamic  just make a function and instead of explicitly putting userPassword you can place the value of the property you want to exclude

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I accomplished it this way  as an example from my Redux reducer    const clone        state     delete clone action id    return clone    In other words   const clone        originalObject      note  original object is not altered delete clone unwantedKey               or use clone unwantedKey or any other applicable syntax return clone                           the original object without the unwanted key

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The solutions above using structuring do suffer from the fact that you have an used variable  which might cause complaints from ESLint if you re using that   So here are my solutions   const src     a  1  b  2   const result   Object keys src     reduce  acc  k    gt  k      b    acc        acc   k   src k           On most platforms  except IE unless using Babel   you could also do   const src     a  1  b  2   const result   Object fromEntries    Object entries src  filter k   gt  k      b

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const x    obj1  1  pass  2  obj2  3  obj3 26    const objectWithoutKey    object  key    gt      const   key   deletedKey     otherKeys    object    return otherKeys     console log objectWithoutKey x   pass

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What about this  I never found this patter around but I was just trying to exclude one or more properties without the need of creating an extra object  This seems to do the job but there are some side effects I m not able to see  For sure is not very readable   const postData        token   secret-token      publicKey   public is safe      somethingElse  true      const a              token     rest    postData    gt   rest             a       publicKey   public is safe      somethingElse  true

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Here s an option for omitting dynamic keys that I believe has not been mentioned yet   const obj     1  1  2  2  3  3  4  4    const removeMe   1   const    removeMe   removedKey     newObj     obj    removeMe is aliased as removedKey and ignored  newObj becomes   2  2  3  3  4  4    Note that the removed key does not exist  the value was not just set to undefined

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If you use Babel you can use the following syntax to copy property b from x into variable b and then copy rest of properties into variable y   let x    a  1  b  2  c  3  z 26   let  b     y    x    and it will be transpiled into    use strict    function  objectWithoutProperties obj  keys      var target         for  var i in obj        if  keys indexOf i   gt   0  continue      if   Object prototype hasOwnProperty call obj  i   continue      target i    obj i         return target     var x     a  1  b  2  c  3  z  26    var b   x b   var y    objectWithoutProperties x    b

User · Answer

I recently did it this very simple way   const obj    a  1  b  2       z 26     just using spread operator to separate the unwanted property   const  b     rest    obj       and object assign to take only the  rest  part   const newObj   Object assign         rest

User · Answer

If you use Ramda you can use its omit and clone functions to make a deep clone of your object and omit the unnecessary fields  var object    a  1  b  2  c  3  y 25  z 26   R clone R omit   quot z quot    quot y quot    object

User · Answer

You can write a simple helper function for it  Lodash has a similar function with the same name  omit  function omit obj  omitKey      return Object keys obj  reduce  result  key    gt        if key     omitKey           result key    obj key             return result               omit  a  1  b  2  c  3    c        a  1  b  2    Also  note that it is faster than Object assign and delete then  http   jsperf com omit-key

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Here are my two cents  on Typescript  slightly derived from  Paul s answer and using reduce instead  function objectWithoutKey object  object  keys  string          return keys reduce  previousValue  currentValue    gt                ts-ignore         const   currentValue   undefined     clean    previousValue          return clean        object        usage console log objectWithoutKey  a  1  b  2  c  3     a    b

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I don t know exactly what you want to use this for  so I m not sure if this would work for you  but I just did the following and it worked for my use case  const newObj      obj   key   undefined

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I use this ESNext one liner   x000D   x000D  const obj     a  1  b  2  c  3  d  4   x000D  const clone       b  c     o      gt  o  obj     remove b and c x000D  console log clone  x000D   x000D   x000D      If you need a general purpose function     x000D   x000D  function omit obj  props    x000D    props   props instanceof Array   props    props  x000D    return eval       props join           o     gt  o  obj    x000D    x000D   x000D     usage x000D  const obj     a  1  b  2  c  3  d  4   x000D  const clone   omit obj    b    c    x000D  console log clone  x000D   x000D   x000D

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Using Object Destructuring   x000D   x000D  const omit    prop     prop         rest      gt  rest  x000D  const obj     a  1  b  2  c  3    x000D  const objWithoutA   omit  a   obj   x000D  console log objWithoutA       b  2  c  3  x000D   x000D   x000D

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You also can use spread operator to do this  const source     a  1  b  2  c  3  z  26   const copy        source       b  undefined          a  1  c  3  z  26

User · Answer

var clone   Object assign      a  1  b  2  c  3    delete clone b    or if you accept property to be undefined   var clone   Object assign      a  1  b  2  c  3    b  undefined

User · Answer

To add to Ilya Palkin s answer  you can even dynamically remove keys   const x    a  1  b  2  c  3  z 26    const objectWithoutKey    object  key    gt      const   key   deletedKey     otherKeys    object    return otherKeys     console log objectWithoutKey x   b         a  1  c  3  z 26  console log x       a  1  b  2  c  3  z 26     Demo in Babel REPL  Source    https   twitter com ydkjs status 699845396084846592

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For those who can t use ES6  you can use lodash or underscore     omit x   b     Or ramda   R omit  b   x

User · Answer

Hey seems like you run in to reference issues when you re trying to copy an object then deleting a property  Somewhere you have to assign primitive variables so javascript makes a new value   Simple trick  may be horrendous  I used was this  var obj     key1   value1   key2   value2   key3   value3        assign it as a new variable for javascript to cache var copy   JSON stringify obj      reconstitute as an object copy   JSON parse copy      now you can safely run delete on the copy with completely new values delete copy key2  console log obj     output   key1   value1   key2   value2   key3   value3   console log copy     output   key1   value1   key3   value3

[javascript] How can I clone a JavaScript object except for one key?

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