一定量スクロールすると表示されるナビゲーション

jquery.navControl.js

/**
 * @param {String} el       対象のセレクター ※必須
 * @param {Number} position 特定の位置 ※必須
 * @param {Number} height   スライドの量 ※必須
 * @param {Number} time   スクロールするスピード [初期値=200]
 * @param {String} easing イージング [初期値='swing']
 */
function NavControl(el,position,height,time,easing){
	this.$el = $(el);
	this.position = position;
	this.height = height;
	this.time = time || 200;
	this.easing = easing || 'linear';
	this.$window = $(window);
	this.event();
}

NavControl.prototype = {

	event: function(){
		var that = this;
		this.$window.on('scroll', function(){
			var scrollTop = that.getScrollTop(this);
			that.decidePosition(scrollTop);
		});
	},

	getScrollTop: function(self){
		return $(self).scrollTop();
	},

	decidePosition: function(scrollTop){
		if( scrollTop > this.position ){
			this.animation(0);
		}else{
			this.animation(this.height);
		}
	},

	animation: function(n){
		this.$el.stop().animate({top: n}, this.time, this.easing);
	}
}

$(function(){
    //init
    new NavControl('selector', 136, -50);
    //('selector', display position, Quantity of the slide, time ,easing)
});