[JustSomeNobody]

Not familiar with react and barely JavaScript, but why is <a onClick="function('value')"> bad? I mean as longs as the function calls a function on another module and doesn't contain any more logic than that. The other module remains testable, and the only logic in the UI is a function call. If the interface of the module changes, sure the UI would have to change, but I tend to think people over think things at this point (my opinion and I hope it doesn't distract from my original question).

[mtrimpe]

As far as I'm concerned <a onClick="function('value')"> was bad because 'function' was a global variable reference.

I don't think that's the case for React though so I'm not sure if the GP saw some other drawbacks in it (apart from the aesthetic of separating logic from presentation.)

[Bahamut]

In React, you would do <a onClick={this.props.foo('value')}> (for example) - JSX would interpolate that and set up the appropriate click binding, and the function is local to the component.