add onVisible callback

[willian12345]

add onVisible callback callback will be called when the element in viewport

it's useful to extend functionally outside. like this example in my project, I can do anything i want on 'elem'

window['lazyshow'] = lazyload({onVisible: function(elem){
            $(elem).addClass('fadeIn');
        }})```

[vvo]

Thanks for the PR.

I am sorry it's undocumented but already exists.

What you want to do is almost already feasible like this:

lazyload(ADOMElement, function onVisible() {
  // will be called when ADOMelement becomes visible
  // src will not be changed for you
});

You can also use vvo/in-viewport because this example is just an alias of in-viewport.

Do you think that's sufficient or do you really need this functionnality?

I think you could just use the standard lazyload and then if in the need for a callback on every element you can lazyload(ADOMElement, function onVisible() {});

If you really need this functionnality as the code is very small, we can integrate it, bust you need to add a test.

The test paragraph of the readme is pretty self explanatory and will be a good start.

Thanks.

[willian12345]

Hi, Thanks for replied. I have read the lazyload.js and in-viewport.js Actually, I use the lazyload like your said in the beginning

lazyload(ADOMElement, function onVisible() {
  // will be called when ADOMelement becomes visible
  // src will not be changed for you
});

But i have to write the lazyload' logic in the in-viewport's callback And we often add some animations to the lazyload dom even we use any other lazyloader

Now i used your lazyload in my project In this page http://crapi.4gshu.com:8096/rongshuxia/excellent.html

The test, er.......