How to set state with spread operators, when using variables for keys?

spread operator react state
object spread operator
react spread operator
spread operator react array
react update state array of objects
react setstate dictionary
setstate react
react spread operator add to array

I have a certain piece of state like:

    this.state = {
     receipts: {
       qwer12r: {color: 'red', size: '20'}
       qas123e: {color: 'green', size: '21'}
    }
   };

these values are collected from two different forms. hence the keys correspond to different form IDs. The forms have drop-downs from where I successfully return the formID and the selected value.

But, using the formID, I want to burrow into the formID object and update only one of the properties.

The components are structured such that the children are the forms, and the parent is a form creator / duplicator.

This implies that the change functions need to be passed down to the children to retrieve their formID, and correspondingly update the correct state, belonging to the correct form.

I have tried the spread operator in many different ways, all having failed to produce the expected result.

In the parent Here's what I've already tried:

handleChange(formNumber, value) {
    this.setState(prevState => ({
      receipts: {
        ...prevState.receipts,
        [formNumber]: {
          ...prevState.formNumber,
          color: value
        }
      }
    }));

and this:

handleChange(formNumber, value) {
    this.setState(prevState => ({
      receipts: {
        ...prevState.receipts,
        [formNumber]: {
          ...`prevState.receipts.${formNumber}`,
          color: value
        }
      }
    }));

and this:

handleChange(formNumber, value) {
    this.setState(prevState => ({
      receipts: {
        ...prevState.receipts,
        [formNumber]: {
          ...`prevState.${formNumber}`,
          color: value
        }
      }
    }));

In the Child: Here is handler attached to the onChange of the color dropdown in the form:

onChange={value =>this.handleValueChange(this.props.formNumber, value)}

and here is that method definition:

handleValueChange= (formId, value) => {
    this.props.handleformColorChange(formId, value);
  };

If the child form calls the handleChange method like handleChange('qwer12r', 'blue'),

the expected result:

this.state = {
receipts: {
   qwer12r: {color: 'blue', size: '20'}
   qas123e: {color: 'green', size: '21'}
}
};

Access receipts with bracket notation

handleChange(formNumber, value) {
    this.setState(prevState => ({
        receipts: {
            ...prevState.receipts,
            [formNumber]: {
                ...prevState.receipts[formNumber],
                color: value
            }
        }
    }));

Using the spread operator in React setState, I'm currently building an app using React.js and ran into an issue that had me stumped. When a button in the app is clicked, I needed a piece of� Make sure to set state correctly and to use the latest state. Here are some examples from the official documentation: // Wrong this.setState({ counter: this.state.counter + this.props.increment }); Instead you should use a function which takes the previous state as a first argument. // Correct this.setState((state, props) => ({ counter: state.

This might be helpful.

handleChange(formId, value) = () => {
   this.setState({
       [formId] : {
          ...this.state[formId],
          color: value
       }
   )}
}

Understanding this.setState({ [name]: value}), Of course the variable names (const key and const value) do not have to allow you concatenate strings without having to use the + operator . Spread operator allows an iterable to expand in places where 0+ arguments are expected. It is mostly used in the variable array where there is more than 1 values are expected. It allows us the privilege to obtain a list of parameters from an array. Syntax of Spread operator is same as Rest parameter but it works completely opposite of it. Syntax:

You can retrieve the property by bracket notation, Below is the simple implementation for same.

class Parent extends Component {
  constructor() {
    super()
    this.state = { receipts: { firstForm: { color: "" } } }
    this.handleChange = this.handleChange.bind(this);
  }

  handleChange(formNumber, value) {
    this.setState(prevState => ({
         receipts: {
          ...prevState.receipts,
          [formNumber]: {
            ...prevState[formNumber],
            color: value
          }
       }
    }));
  }

  render() {
    console.log(this.state)
    return (
      <Child formNumber="firstForm"
        handleformColorChange={this.handleChange}
        value={this.state.receipts.firstForm.color}></Child>
    )
  }
}

Using Object Spread Operator, #Using Object Spread Operator. Since one of the core tenets of Redux is to never mutate state, you'll often find yourself using Object.assign() to create copies of� I’m currently building an app using React.js and ran into an issue that had me stumped. When a button in the app is clicked, I needed a piece of the state to be updated. Sounds easy enough. The

How to update state using setState method of the useState hook in , setState of React useState hook replace state instead of merging it like this. You should be working on your state variable outside of the setState function. A spread operator takes an object and spread its key, like so. Spread operator. While rest parameters use the rest operator to combine zero or more parameters into a single array parameter, the spread operator does just the opposite. It separates an array into zero or more parameters. But before we get into how the spread operator works, lets first take a look at the ES5 code it is intending to replace.

React: prevState vs. Spread Operator or Both? - JavaScript, What's the difference between these two setState commands? you have the correct state values, you need to use the callback form of setState realized it's a variable in a callback, not a key word or specific function (right?) Spread a key-value pair across multiple columns. Development on spread () is complete, and for new code we recommend switching to pivot_wider (), which is easier to use, more featureful, and still under active development. df %>% spread (key, value) is equivalent to df %>% pivot_wider (names_from = key, values_from = value) See more details in vignette ("pivot").

How to update nested props in reducer? � Issue #432 � reduxjs/redux , I can't figure out the correct way to update nested property in reducers state. FYI, I have a work-in-progress set of new pages for the Redux docs on When I try to use this spread operator on the state it gives me the error, "object of type If your state object is a dictionary where the keys are variable Ids instead of known � By using the JavaScript spread operator, you can spread all key value pairs of the initial state object to the initial state of the component. That works with multiple properties in the state object too.