[Solved]-React this.setState is not a function-Reactjs

Use from arrow function to handle action.

This is mainly incompatibility problem between react, react-dom, and enzyme.

Try install the following as I did to solve the problem:

[...]
    "react": "^18.0.0-beta-f320ef88f-20211116",
    "react-dom": "16.14.0",
    "enzyme": "^3.11.0",
    "enzyme-adapter-react-16": "^1.15.6"
[...]

In my case, the problem was that I was sending the state and setstate as props to a child component but there was a typo in setstate

If you're doing this and still having an issue, my problem is I was calling two variables the same name.

I had companies as an object brought in from Firebase, and then was trying to call this.setState({companies: companies}) - it wasn't working for obvious reasons.

I have the same error of

TypeError: setState is not a function

but the cause is silly. Posting it as a response here to hopefully save people who might be making the same mistake.

Instead of

  const { state, setState } = React.useState(false);

Use

  const [ state, setState ] = React.useState(false);

Square brackets and not curly brackets!

Here THIS context is getting changed. Use arrow function to keep context of React class.

        VK.init(() => {
            console.info("API initialisation successful");
            VK.api('users.get',{fields: 'photo_50'},(data) => {
                if(data.response){
                    this.setState({ //the error happens here
                        FirstName: data.response[0].first_name
                    });
                    console.info(this.state.FirstName);
                }

            });
        }, function(){
        console.info("API initialisation failed");

        }, '5.34');

Now in react with es6/7 you can bind function to current context with arrow function like this, make request and resolve promises like this :

listMovies = async () => {
 const request = await VK.api('users.get',{fields: 'photo_50'});
 const data = await request.json()
 if (data) {
  this.setState({movies: data})
 }
}

With this method you can easily call this function in the componentDidMount and wait the data before render your html in your render function.

I don't know the size of your project but I personally advise against using the current state of the component to manipulate datas. You should use external state like Redux or Flux or something else for that.

You no need to assign this to a local variable if you use arrow function. Arrow functions takes binding automatically and you can stay away with scope related issues.

Below code explains how to use arrow function in different scenarios

componentDidMount = () => {

    VK.init(() => {
        console.info("API initialisation successful");
        VK.api('users.get',{fields: 'photo_50'},(data) => {
            if(data.response){
                that.setState({ //this available here and you can do setState
                    FirstName: data.response[0].first_name
                });
                console.info(that.state.FirstName);
            }
        });
    }, () => {
        console.info("API initialisation failed");

    }, '5.34');
 },

Now ES6 have arrow function it really helpful if you really confuse with bind(this) expression you can try arrow function

This is how I do.

componentWillMount() {
        ListApi.getList()
            .then(JsonList => this.setState({ List: JsonList }));
    }

 //Above method equalent to this...
     componentWillMount() {
         ListApi.getList()
             .then(function (JsonList) {
                 this.setState({ List: JsonList });
             }.bind(this));
 }

use arrow functions, as arrow functions point to parent scope and this will be available. (substitute of bind technique)

You just need to bind your event

for ex-

// place this code to your constructor

this._handleDelete = this._handleDelete.bind(this);

// and your setState function will work perfectly

_handleDelete(id){

    this.state.list.splice(id, 1);

    this.setState({ list: this.state.list });

    // this.setState({list: list});

}

you could also save a reference to this before you invoke the api method:

componentDidMount:function(){

    var that = this;

    VK.init(function(){
        console.info("API initialisation successful");
        VK.api('users.get',{fields: 'photo_50'},function(data){
            if(data.response){
                that.setState({ //the error happens here
                    FirstName: data.response[0].first_name
                });
                console.info(that.state.FirstName);
            }
        });
    }, function(){
        console.info("API initialisation failed");

    }, '5.34');
},

React recommends bind this in all methods that needs to use this of class instead this of self function.

constructor(props) {
    super(props)
    this.onClick = this.onClick.bind(this)
}

 onClick () {
     this.setState({...})
 }

Or you may to use arrow function instead.

You can avoid the need for .bind(this) with an ES6 arrow function.

VK.api('users.get',{fields: 'photo_50'},(data) => {
        if(data.response){
            this.setState({ //the error happens here
                FirstName: data.response[0].first_name
            });
            console.info(this.state.FirstName);
        }

    });