Why does state change on its own even though I'm not assigning anything?

Question

React

In this code, this.setState is simply written and I do not assign anything inside, however, the state changes. What's happening?

changeHandler = (value, controlName, controls) => {
    const formControls = controls.slice();
    const control = formControls[controlName]

    control.touched = true
    control.value = value
    control.valid = validate(control.value, control.validation)

    formControls[controlName] = control  
    this.setState({       
    })
  }