Undefined variable, scoping issue

Question

I am trying to update the state of an object in an array in React using Immutability Helpers.

  handleChange = (itemInput, itemNum = null) => event => {
    this.setState({
      rows: update(this.state.rows, {
        itemNum: {[itemInput]: {$set: event.target.value}},
      })
    });
  }

I get an error "Uncaught TypeError: Cannot read property 'update' of undefined". The reason is itemNum is undefined and I can't figure out why(I know it is undefined since if I replace it with 1, for example, the code works. This is probably some scope issue :/ Thanks for any suggestions on how to fix that!

Just to clarify that the variables are all defined and I can console.log them before the this.setState.

update comes from https://reactjs.org/docs/update.html . I used the example under "Nested collections" where they have hardcoded the value 2, and in my case, it has to be itemNum

Basically, what I am trying to do is

this.state.rows[itemNum][itemInput] = event.target.value

but I guess React makes it a bit complicated for me...

In the constructor I have

this.handleChange = this.handleChange.bind(this);

And I call the onChange with onChange={this.handleChange("searchType", i)}

As per documentation itemNum has to be index and itemInput has to be array, just wanna look on that part — Garry
– Garry, Commented Jun 5, 2019 at 15:43

Valerii · Accepted Answer · 2019-06-05 17:05:36Z

1

handleChange = (itemInput, itemNum = null) => event => {
    this.setState({
        rows: update(this.state.rows, {
            [itemNum]: {[itemInput]: {$set: event.target.value}},
        })
    });
};

answered Jun 5, 2019 at 17:05

Valerii

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