Storing an object in state of a React component

Question

Is it possible to store an object in the state of a React component  If yes  then how can we change the value of a key in that object using setState  I think it s not syntactically allowed to write something like   this setState   abc xyz   new value        On similar lines  I ve another question  Is it okay to have a set of variables in a React component such that they can be used in any method of the component  instead of storing them in a state    You may create a simple object that holds all these variables and place it at the component level  just like how you would declare any methods on the component    Its very likely to come across situations where you include a lot of business logic into your code and that requires using many variables whose values are changed by several methods  and you then change the state of the component based on these values    So  instead of keeping all those variables in the state  you only keep those variables whose values should be directly reflected in the UI   If this approach is better than the first question I wrote here  then I don t need to store an object in the state

User · Answer

this setState  abc   xyz   new value      will NOT work  as state abc will be entirely overwritten  not merged   This works for me   this setState  previousState    gt      previousState abc xyz    blurg     return previousState        Unless I m reading the docs wrong  Facebook recommends the above format  https   facebook github io react docs component-api html  Additionally  I guess the most direct way without mutating state is to directly copy by using the ES6 spread rest operator   const newState        this state abc       deconstruct state abc into a new object-- effectively making a copy newState xyz    blurg   this setState newState

User · Answer

You can use ES6 spread on previous values in the object to avoid overwrite  this setState        abc                   this state abc              xyz   new value

User · Answer

In addition to kiran s post  there s the update helper  formerly a react addon   This can be installed with npm using npm install immutability-helper  import update from  immutability-helper    var abc   update this state abc       xyz    set   foo        this setState  abc  abc      This creates a new object with the updated value  and other properties stay the same   This is more useful when you need to do things like push onto an array  and set some other value at the same time   Some people use it everywhere because it provides immutability    If you do this  you can have the following to make up for the performance of   shouldComponentUpdate  function nextProps  nextState      return this state abc     nextState abc         and compare any props that might cause an update

User · Answer

Easier way to do it in one line of code  this setState   object       this state object  objectVarToChange  newData

User · Answer

this setState   abc xyz   new value      syntax is not allowed  You have to pass the whole object    this setState  abc   xyz   new value        If you have other variables in abc  var abc   this state abc  abc xyz    new value   this setState  abc  abc     You can have ordinary variables  if they don t rely on this props and this state

User · Answer

Even though it can be done via immutability-helper or similar I do not wan t to add external dependencies to my code unless I really have to  When I need to do it I use Object assign  Code   this setState   abc   Object assign     this state abc    xyz   new value        Can be used on HTML Event Attributes as well  example   onChange  e   gt  this setState   abc   Object assign     this state abc   xyz    new value

[javascript] Storing an object in state of a React component?

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