How to replace array element by specific index number in react

Question

I have an array of [false,true,false,false,true] I want to change these boolean values based on index number . I tried my best but didn't find a solution to resolve this issue. I want to be done this in react .

    this.setState({
       stateValue:[...array,array[0]=true]
   })

I tried with this solution but it can add value at the end of array

Does this answer your question? How do I modify the value of an array of Bool in React? — Heretic Monkey
– Heretic Monkey, Commented Nov 6, 2020 at 20:39
You can do this with array map(). Before learning react it is recommended that you have a solid understanding of advanced array methods such as map, filter, reduce & other ES6+ features. — alewis729
– alewis729, Commented Nov 6, 2020 at 20:40
can you provide a more complete version of your code? please see How to create a Minimal, Reproducible Example — andersryanc
– andersryanc, Commented Nov 6, 2020 at 21:09

andersryanc · Accepted Answer · 2020-11-06 20:45:29Z

0

I would do something like:

this.setState(prevState => {
  const newStateValue = [...prevState.stateValue]
  newStateValue[desired_index] = boolean_value
  return {
    ...prevState,
    stateValue: newStateValue,
  }
})

it's good practice when modifying state to do so in an immutable way, by first copying the data, manipulating the new copy and then setting that back into state.

using the prevState => {} callback to setState also helps to ensure the state changes get applied in the correct order if they occur in quick succession

answered Nov 6, 2020 at 20:45

andersryanc

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3 Comments

React Guy Over a year ago

actually, it not updating state

andersryanc Over a year ago

it's just sample code, obviously some of the variables are undefined / don't match up exactly how you would use it as just a drop in... did you change out the values with what you were trying to do?

React Guy Over a year ago

Yes, I changed values but state is not updating actually

akeempositive · Accepted Answer · 2020-11-06 20:51:11Z

-1

Or this...

     var newArray = this.state.statevalue;
     newArray[i] = true;
     this.setState({stateValue: newArray});

answered Nov 6, 2020 at 20:51

akeempositive

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1 Comment

Pipe Over a year ago

This will also modify the current this.state.stateValue value... thats a bad practice

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