jQuery - If .class is visible viewport

script.js

jQuery( window ).load( function () {
	jQuery.fn.isOnScreen = function() {
		var win = jQuery( window );

		var viewport = {
			top: win.scrollTop(),
			left: win.scrollLeft()
		};
		
		viewport.right = viewport.left + win.width();
		viewport.bottom = viewport.top + win.height();
		var bounds = this.offset();
		bounds.right = bounds.left + this.outerWidth();
		bounds.bottom = bounds.top + this.outerHeight();
		return ( ! ( viewport.right < bounds.left || viewport.left > bounds.right || viewport.bottom < bounds.top || viewport.top > bounds.bottom ) );
	};

	if ( jQuery( '.sc-play-btn' ).isOnScreen() ) {
		jQuery( '.sc-play-btn' ).trigger( 'click' );
	}
} );