Delete item from state array in react

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});
}