javascript - 缩小滚动图像 - jQuery

Question

我想在滚动经过它的顶部时立即将我的标题图像大小缩小到 50% 宽度/高度。最好它会过渡而不是突然跳到一半大小。

我在下面整理了一些东西，但过渡发生得太晚了。我如何解决这个问题，以便在我通过它时立即发生？

/*!
 * classie - class helper functions
 * from bonzo https://github.com/ded/bonzo
 * 
 * classie.has( elem, 'my-class' ) -> true/false
 * classie.add( elem, 'my-new-class' )
 * classie.remove( elem, 'my-unwanted-class' )
 * classie.toggle( elem, 'my-class' )
 */

/*jshint browser: true, strict: true, undef: true */
/*global define: false */

( function( window ) {

'use strict';

// class helper functions from bonzo https://github.com/ded/bonzo

function classReg( className ) {
  return new RegExp("(^|\\s+)" + className + "(\\s+|$)");
}

// classList support for class management
// altho to be fair, the api sucks because it won't accept multiple classes at once
var hasClass, addClass, removeClass;

if ( 'classList' in document.documentElement ) {
  hasClass = function( elem, c ) {
    return elem.classList.contains( c );
  };
  addClass = function( elem, c ) {
    elem.classList.add( c );
  };
  removeClass = function( elem, c ) {
    elem.classList.remove( c );
  };
}
else {
  hasClass = function( elem, c ) {
    return classReg( c ).test( elem.className );
  };
  addClass = function( elem, c ) {
    if ( !hasClass( elem, c ) ) {
      elem.className = elem.className + ' ' + c;
    }
  };
  removeClass = function( elem, c ) {
    elem.className = elem.className.replace( classReg( c ), ' ' );
  };
}

function toggleClass( elem, c ) {
  var fn = hasClass( elem, c ) ? removeClass : addClass;
  fn( elem, c );
}

var classie = {
  // full names
  hasClass: hasClass,
  addClass: addClass,
  removeClass: removeClass,
  toggleClass: toggleClass,
  // short names
  has: hasClass,
  add: addClass,
  remove: removeClass,
  toggle: toggleClass
};

// transport
if ( typeof define === 'function' && define.amd ) {
  // AMD
  define( classie );
} else {
  // browser global
  window.classie = classie;
}

})( window );








/**
 * cbpAnimatedHeader.min.js v1.0.0
 * http://www.codrops.com
 *
 * Licensed under the MIT license.
 * http://www.opensource.org/licenses/mit-license.php
 * 
 * Copyright 2013, Codrops
 * http://www.codrops.com
 */
var cbpAnimatedHeader=(function(){var b=document.documentElement,g=document.querySelector(".cbp-af-header"),e=false,a=300;function f(){window.addEventListener("scroll",function(h){if(!e){e=true;setTimeout(d,250)}},false)}function d(){var h=c();if(h>=a){classie.add(g,"cbp-af-header-shrink")}else{classie.remove(g,"cbp-af-header-shrink")}e=false}function c(){return window.pageYOffset||b.scrollTop}f()})();

body {
  text-align:center;
  padding:0;
  margin:0;
}

img {
  padding-top:60px
}

.cbp-af-header {
	position: fixed;
	top: 0;
	left: 0;
	width: 100%;
	background: #f6f6f6;
	z-index: 10000;
	height: 200px;
	overflow: hidden;
	-webkit-transition: height 0.3s;
	-moz-transition: height 0.3s;
	transition: height 0.3s;
}

.cbp-af-header .cbp-af-inner {
	width: 90%;
	max-width: 69em;
	margin: 0 auto;
	padding: 0 1.875em;
}

.cbp-af-header h1,
.cbp-af-header nav {
	display: inline-block;
	position: relative;
}

 /* We just have one-lined elements, so we'll center the elements with the line-height set to the height of the header */
.cbp-af-header h1,
.cbp-af-header nav a {
	line-height: 200px;
}

.cbp-af-header h1 {
	text-transform: uppercase;
	color: #333;
	letter-spacing: 4px;
	font-size: 4em;
	margin: 0;
	float: left;
}

.cbp-af-header nav {
	float: right;
}

.cbp-af-header nav a {
	color: #aaa;
	font-weight: 700;
	margin: 0 0 0 20px;
	font-size: 1.4em;
}

.cbp-af-header nav a:hover {
	color: #333;
}

/* Transitions and class for reduced height */
.cbp-af-header h1,
.cbp-af-header nav a {
	-webkit-transition: all 0.3s;
	-moz-transition: all 0.3s;
	transition: all 0.3s;
}

.cbp-af-header.cbp-af-header-shrink {
	height: 90px;
}

.cbp-af-header.cbp-af-header-shrink h1,
.cbp-af-header.cbp-af-header-shrink nav a {
	line-height: 90px;
}

.cbp-af-header.cbp-af-header-shrink h1 {
	font-size: 2em;
}

/* Example Media Queries */
@media screen and (max-width: 55em) {
	
	.cbp-af-header .cbp-af-inner {
		width: 100%;
	}

	.cbp-af-header h1,
	.cbp-af-header nav {
		display: block;
		margin: 0 auto;
		text-align: center;
		float: none;
	}

	.cbp-af-header h1,
	.cbp-af-header nav a {
		line-height: 115px;
	}

	.cbp-af-header nav a {
		margin: 0 10px;
	}

	.cbp-af-header.cbp-af-header-shrink h1,
	.cbp-af-header.cbp-af-header-shrink nav a {
		line-height: 45px;
	}

	.cbp-af-header.cbp-af-header-shrink h1 {
		font-size: 2em;
	}

	.cbp-af-header.cbp-af-header-shrink nav a {
		font-size: 1em;
	}
}

@media screen and (max-width: 32.25em) {
	.cbp-af-header nav a {
		font-size: 1em;
	}
}

@media screen and (max-width: 24em) {
	.cbp-af-header nav a,
	.cbp-af-header.cbp-af-header-shrink nav a {
		line-height: 1;
	}
}

<div class="cbp-af-header">
				<div class="cbp-af-inner">
          <img src="http://placehold.it/600x200">
        </div>
</div>

<p>
test
</p>

<p>
test
</p>

<p>
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</p>

<p>
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</p>

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</p>

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</p>

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</p>

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</p>

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</p>

Answer 1

更新您的标题动画脚本 (cbpAnimatedHeader.min.js) 以将标题大小调整为 1 像素而不是 300。

/**
 * cbpAnimatedHeader.js v1.0.0
 * http://www.codrops.com
 *
 * Licensed under the MIT license.
 * http://www.opensource.org/licenses/mit-license.php
 * 
 * Copyright 2013, Codrops
 * http://www.codrops.com
 */
var cbpAnimatedHeader = (function() {

    var docElem = document.documentElement,
        header = document.querySelector( '.cbp-af-header' ),
        didScroll = false,
        changeHeaderOn = 1; // this is initially set to 300

    function init() {
        scrollPage();
        window.addEventListener( 'scroll', function( event ) {
            if( !didScroll ) {
                didScroll = true;
                setTimeout( scrollPage, 250 );
            }
        }, false );
    }

    function scrollPage() {
        var sy = scrollY();
        if ( sy >= changeHeaderOn ) {
            classie.add( header, 'cbp-af-header-shrink' );
        }
        else {
            classie.remove( header, 'cbp-af-header-shrink' );
        }
        didScroll = false;
    }

    function scrollY() {
        return window.pageYOffset || docElem.scrollTop;
    }

    init();

})();