The script clones the nvm repository to ~/.nvm and adds the source line to your profile (~/.bash_profile, ~/.zshrc, ~/.profile, or ~/.bashrc).
When we declare callback as onClick={this.fetchUsers} every render call will pass the same onClick reference to the button.
At the time, when we use onClick={() => this.fetchUsers()} each render call will init new function () => this.fetchUsers() and will pass it to the button onClick prop. It means, that nextProp.onClick and prop.onClick won't be equal and even if we use a PureComponent instead of button it will be re-rendered.