nl_tokens: 显示图片
pl_tokens: function ( othis , scroll ) { //计算滚动所在容器的可视高度 var height = notDocment ? ( scroll || scrollElem ) . height ( ) : $ ( window ) . height ( ) ; var start = scrollElem . scrollTop ( ) , end = start + height ; that . lazyimg . elem = $ ( elem ) ; if ( othis ) { show ( othis , height ) ; } else { //计算未加载过的图片 for ( var i = 0 ; i < that . lazyimg . elem . length ; i ++ ) { var item = that . lazyimg . elem . eq ( i ) , elemTop = notDocment ? function ( ) { return item . offset ( ) . top - scrollElem . offset ( ) . top + start ; } ( ) : item . offset ( ) . top ; show ( item , height ) ; index = i ; //如果图片的top坐标，超出了当前屏，则终止后续图片的遍历 if ( elemTop > <mask> ) break ; } } }