外部链接的Javascript无法正常工作

Question

我看了this关于如何使用JavaScript和jQuery编写真正高效的视差效果的两部分教程

当我将JS直接放入html文件时，它可以完美地工作，但是当我在外部链接它时，它不起作用。为什么？

Working version (internal JS)

非工作版本

(function ($) {

    var $container = $(".parallax");
    var $divs = $container.find("div.parallax-background");
    var thingBeingScroll = document.body;
    var liHeight = $divs.eq(0).closest("li").height();
    var diffHeight = $divs.eq(0).height() - liHeight;
    var len = $divs.length;

    var i, div, li, offset, scroll, top, transform;

    var offsets = $divs.get().map(function (div, d) {
        return $(div).offset();
    });

    var render = function () {

	        top = thingBeingScroll.scrollTop;

	        for (i = 0; i < len; i++) {
	            div = $divs[i];

	            offset = top - offsets[i].top;

	            scroll = ~~((offset / liHeight * diffHeight) * 2);

	            transform = 'translate3d(0px,' + scroll + 'px,0px)';

	            div.style.webkitTransform = transform;
	            div.style.MozTransform = transform;
	            div.style.msTransform = transform;
	            div.style.OTransform = transform;
	            div.style.transform = transform;
	        }
	    };

	    (function loop() {
	        requestAnimationFrame(loop);
	        render();
	    })();

	    (function () {
	        var lastTime = 0;
	        var vendors = ['webkit', 'moz'];
	        for (var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
	            window.requestAnimationFrame = window[vendors[x] + 'RequestAnimationFrame'];
	            window.cancelAnimationFrame =
	              window[vendors[x] + 'CancelAnimationFrame'] || window[vendors[x] + 'CancelRequestAnimationFrame'];
	        }

	        if (!window.requestAnimationFrame)
	            window.requestAnimationFrame = function (callback, element) {
	                var currTime = new Date().getTime();
	                var timeToCall = Math.max(0, 16 - (currTime - lastTime));
	                var id = window.setTimeout(function () { callback(currTime + timeToCall); },
	                  timeToCall);
	                lastTime = currTime + timeToCall;
	                return id;
	            };

	        if (!window.cancelAnimationFrame)
	            window.cancelAnimationFrame = function (id) {
	                clearTimeout(id);
	            };
	    }());

	})(jQuery);

body, ul {
			margin: 0;
			padding: 0;
		}

		body {
			height: 2500px;
		}

		ul li {
			list-style: none;
			overflow: hidden;
			height: 600px;
		}

		.parallax-background {
			height: 700px;
			background-size: cover; 
		}

		.lens {
			background-image: url('http://www.cameraegg.org/wp-content/uploads/2013/04/sigma-art-lenses.jpg');
		}
		.beach {
			background-image: url('https://c1.staticflickr.com/3/2422/3799310645_92dba468ae_b.jpg');
		}
		.wolf {
			background-image: url('http://images.alphacoders.com/102/102853.jpg');
		}
		.flower {
			background-image: url('http://i.imgur.com/Aoo6BAk.jpg');
		}

  <ul class="parallax">
			<li>
				<div class="parallax-background flower"></div>
			</li>
		</ul>

		<h1>Content</h1>

Answer 1

您的parallax.js脚本和parallax.css的路径似乎无效：

<script src="parallax.js" type="parallax.js"></script> <!--Parallax JS-->
<link rel="stylesheet" type="text/css" href="parallax.css"> <!--Parallax CSS-->

转到这些网址（通过点击Chrome中的链接文件），请将我发送到Google的登录页面。尝试更改脚本src并链接href以使用绝对路径，并确保两者都对公众可见。