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/**
* jQuery Unveil
* A very lightweight jQuery plugin to lazy load images
* http://luis-almeida.github.com/unveil
*
* Licensed under the MIT license.
* Copyright 2013 Luís Almeida
* https://github.com/luis-almeida
*/
;(function($) {
$.fn.unveil = function(threshold, callback) {
var $w = $(window),
th = threshold || 0,
retina = window.devicePixelRatio > 1,
attrib = retina? "data-src-retina" : "data-src",
images = this,
loaded;
this.one("unveil", function() {
var source = this.getAttribute(attrib);
source = source || this.getAttribute("data-src");
if (source) {
this.setAttribute("src", source);
if (typeof callback === "function") callback.call(this);
}
});
function unveil() {
var inview = images.filter(function() {
var $e = $(this);
[color=#FF0000]if ($e.is(":hidden")) return;[/color]
var wt = $w.scrollTop(),
wb = wt + $w.height(),
et = $e.offset().top,
eb = et + $e.height();
console.log(wt);
console.log(wb);
console.log(et);
console.log(eb);
[color=#FF0000]return eb >= wt - th && et <= wb + th;[/color]
});
loaded = inview.trigger("unveil");
images = images.not(loaded);
}
$w.on("scroll.unveil resize.unveil lookup.unveil", unveil);
unveil();
return this;
};
})(window.jQuery || window.Zepto);I have a few questions about the above code , sorry for posting the entire code , but I just wanted there to be no missing bits .
In the code above there are three instances where the return statement is used (marked in red), now I quite don’t understand the usage of return statement , i.e. I don’t quite understand whom they are returning what .
The first return statement :
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if ($e.is(":hidden")) return; the second return statement :
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return eb >= wt - th && et <= wb + th;the third return statement :
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return this;returning what to whom ??