How to delete an item from state array?

Question

When using React, you should never mutate the state directly. If an object (or Array, which is an object too) is changed, you should create a new copy.

Others have suggested using Array.prototype.splice(), but that method mutates the Array, so it's better not to use splice() with React.

Easiest to use Array.prototype.filter() to create a new array:

removePeople(e) {
    this.setState({people: this.state.people.filter(function(person) { 
        return person !== e.target.value 
    })});
}

To remove an element from an array, just do:

array.splice(index, 1);

In your case:

removePeople(e) {
  var array = [...this.state.people]; // make a separate copy of the array
  var index = array.indexOf(e.target.value)
  if (index !== -1) {
    array.splice(index, 1);
    this.setState({people: array});
  }
},

Here is a minor variation on Aleksandr Petrov's response using ES6

removePeople(e) {
    let filteredArray = this.state.people.filter(item => item !== e.target.value)
    this.setState({people: filteredArray});
}

Easy Way To Delete Item From state array in react:

when any data delete from database and update list without API calling that time you pass deleted id to this function and this function remove deleted recored from list

export default class PostList extends Component {
  this.state = {
      postList: [
        {
          id: 1,
          name: 'All Items',
        }, {
          id: 2,
          name: 'In Stock Items',
        }
      ],
    }


    remove_post_on_list = (deletePostId) => {
        this.setState({
          postList: this.state.postList.filter(item => item.post_id != deletePostId)
        })
      }
  
}

Use .splice to remove item from array. Using delete, indexes of the array will not be altered but the value of specific index will be undefined

The splice() method changes the content of an array by removing existing elements and/or adding new elements.

Syntax: array.splice(start, deleteCount[, item1[, item2[, ...]]])

var people = ["Bob", "Sally", "Jack"]
var toRemove = 'Bob';
var index = people.indexOf(toRemove);
if (index > -1) { //Make sure item is present in the array, without if condition, -n indexes will be considered from the end of the array.
  people.splice(index, 1);
}
console.log(people);

Edit:

As pointed out by justin-grant, As a rule of thumb, Never mutate this.state directly, as calling setState() afterward may replace the mutation you made. Treat this.state as if it were immutable.

The alternative is, create copies of the objects in this.state and manipulate the copies, assigning them back using setState(). Array#map, Array#filter etc. could be used.

this.setState({people: this.state.people.filter(item => item !== e.target.value);});