Using const in TestCheckbox example

[mauron85]

Why newState is defined as const and in next line you're assigning new field prop to it?

class TestCheckbox extends React.Component {
  state = {
    check1: true,
    check2: false
  };

  handleChange = (field) => {
    const newState = {};
    newState[field] = !this.state[field];
    this.setState(newState);
  };

  render () {
    return (
      <div>
        <Checkbox
          checked={this.state.check1}
          label="Checked option"
          onChange={this.handleChange.bind(this, 'check1')}
        />
        <Checkbox
          checked={this.state.check2}
          label="Unchecked option"
          onChange={this.handleChange.bind(this, 'check2')}
        />
        <Checkbox
          checked
          disabled
          label="Disabled checkbox"
        />
      </div>
    );
  }
}

return <TestCheckbox />;

[javivelasco]

Because technically newState does not mutate it's value. Changing a prop in the object does not mean changing the value of the variable so no runtime errors. In practice you should use something like ImmutableJS to avoid mutating object but we are not doing it here for simplicity.