Fix variable name error on developer api documentation

[jonquach]

Small changes on the developer api.md documentation for the method .getElementAtEvent(e), in the code snippet to get the item that was clicked on.

I believe the variable called here should be item, not firstPoint.

See here

[jcopperfield]

@jonquach I'm not sure your observation is correct. The function in core/core.controllers.js reads:

getElementAtEvent: function(e) {
    return Interaction.modes.single(this, e);
}

Interaction.modes.single returns the return elements.slice(0, 1);, i.e. the first element. Therefore firstPoint correctly specifies the returned element.

[jonquach]

While I tried using it I got an error on this, see this codepen I made.

You can see in the console:

Uncaught ReferenceError: firstPoint is not defined

The object return in item is an Array of ChartElement, and inside it there is no key containing firstPoint.

Maybe I'm using it wrong, do you have any insight on this ?

[jcopperfield]

@jonquach I think I explained myself wrong. IMO it would be better to rename the variable item to firstPoint or firstItem or even firstElement instead of the other way around, so that it is clear what is returned.

[jonquach]

@jcopperfield Oh I see! Sorry I misunderstood. I agree, it seems more consistent, made the changes