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/** jQuery.bsf_appear
* https://github.com/bas2k/jquery.bsf_appear/
* http://code.google.com/p/jquery-bsf_appear/
*
* Copyright (c) 2009 Michael Hixson
* Copyright (c) 2012 Alexander Brovikov
* Licensed under the MIT license (http://www.opensource.org/licenses/mit-license.php)
*/
( function ( $ ) {
$.fn.bsf_appear = function ( fn, options ) {
const settings = $.extend(
{
//arbitrary data to pass to fn
data: undefined,
//call fn only on the first bsf_appear?
one: true,
// X & Y accuracy
accX: 0,
accY: 0,
},
options
);
return this.each( function () {
const t = $( this );
//whether the element is currently visible
t.bsf_appeared = false;
if ( ! fn ) {
//trigger the custom event
t.trigger( 'bsf_appear', settings.data );
return;
}
const w = $( window );
//fires the bsf_appear event when appropriate
const check = function () {
//is the element hidden?
if ( ! t.is( ':visible' ) ) {
//it became hidden
t.bsf_appeared = false;
return;
}
//is the element inside the visible window?
const a = w.scrollLeft();
const b = w.scrollTop();
const o = t.offset();
const x = o.left;
const y = o.top;
const ax = settings.accX;
const ay = settings.accY;
const th = t.height();
const wh = w.height();
const tw = t.width();
const ww = w.width();
if (
y + th + ay >= b &&
y <= b + wh + ay &&
x + tw + ax >= a &&
x <= a + ww + ax
) {
//trigger the custom event
if ( ! t.bsf_appeared )
t.trigger( 'bsf_appear', settings.data );
} else {
//it scrolled out of view
t.bsf_appeared = false;
}
};
//create a modified fn with some additional logic
const modifiedFn = function () {
//mark the element as visible
t.bsf_appeared = true;
//is this supposed to happen only once?
if ( settings.one ) {
//remove the check
w.off( 'scroll', check );
const i = $.inArray( check, $.fn.bsf_appear.checks );
if ( i >= 0 ) $.fn.bsf_appear.checks.splice( i, 1 );
}
//trigger the original fn
fn.apply( this, arguments );
};
//bind the modified fn to the element
if ( settings.one )
t.one( 'bsf_appear', settings.data, modifiedFn );
else t.bind( 'bsf_appear', settings.data, modifiedFn );
//check whenever the window scrolls
w.on( 'scroll', check );
//check whenever the dom changes
$.fn.bsf_appear.checks.push( check );
//check now
check();
} );
};
//keep a queue of bsf_appearance checks
$.extend( $.fn.bsf_appear, {
checks: [],
timeout: null,
//process the queue
checkAll() {
let length = $.fn.bsf_appear.checks.length;
if ( length > 0 ) {
while ( length-- ) {
$.fn.bsf_appear.checks[ length ]();
}
}
},
//check the queue asynchronously
run() {
if ( $.fn.bsf_appear.timeout ) {
clearTimeout( $.fn.bsf_appear.timeout );
$.fn.bsf_appear.timeout = setTimeout(
$.fn.bsf_appear.checkAll,
20
);
} else {
$.fn.bsf_appear.timeout = setTimeout(
$.fn.bsf_appear.checkAll,
20
);
}
},
} );
//run checks when these methods are called
$.each(
[
'append',
'prepend',
'after',
'before',
'attr',
'removeAttr',
'addClass',
'removeClass',
'toggleClass',
'remove',
'css',
'show',
'hide',
],
function ( i, n ) {
const old = $.fn[ n ];
if ( old ) {
$.fn[ n ] = function () {
const r = old.apply( this, arguments );
$.fn.bsf_appear.run();
return r;
};
}
}
);
} )( jQuery );