How to update a value in array Reactjs

Question

I have a fixed array(9) and I want to update the value of the array, this works perfectly but I want to optimize the code:

constructor (props) {
  super();
  this.state ={
    token: "X",
    val: ["","","","","","","","",""]
  };
}

intelligentComputerPlay () {
  this.setState({
    val: [
      this.state.token,
      this.state.val[1],
      this.state.val[2],
      this.state.val[3],
      this.state.val[4],
      this.state.val[5],  
      this.state.val[6],  
      this.state.val[7],  
      this.state.val[8]
    ];
  });

Could you expand on what is the general goal? This seems like a very wrong approach, but we cannot suggest anything better without knowing the general context. — Kamil Solecki
– Kamil Solecki, Commented Feb 10, 2018 at 22:14
@KamilSolecki in intelligentComputerPlay () method i just change the first value but i have written all the elements of the list, i need just updates the value that will be changing in the list. Is it possible? — Amine Sehaba
– Amine Sehaba, Commented Feb 10, 2018 at 22:43

Striped · Accepted Answer · 2018-02-10 22:51:47Z

1

I think this could work.

this.setState(prevState => ({
     val: [token, ...prevState.val.slice(1, prevState.val.length - 1)]
}));

edited Feb 10, 2018 at 22:51

answered Feb 10, 2018 at 22:17

Striped

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2 Comments

Amine Sehaba Over a year ago

how to write it if i want to change the third element for example?

Striped Over a year ago

val: [...prevState.val.slice(0, 3), token, ...prevState.val.slice(5, prevState.val.length - 1)]

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