// external js: masonry.pkgd.js, imagesloaded.pkgd.js
// init Masonry
var $grid = $('.grid').masonry({
itemSelector: '.grid-item',
percentPosition: true,
gutter: 20,
columnWidth: '.grid-sizer'
});
// layout Masonry after each image loads
$grid.imagesLoaded().progress( function() {
$grid.masonry();
});