从 WordPress 3.9.x 升级至 4.x 之后，访问首页源代码，发现头部无缘无故多了一大堆代码，可以判断肯定是 WordPress 自带的，因为之前的旧版本并没有。从“window._wpemojiSettings”字眼中可以看出这应该是关于表情的，我的小站不用表情，即使用也不会用 WP 系统自带的，所以这堆代码对我而言毫无用处，放在首页头部还会影响我的网页加载速度，绝对要去除！

<link rel='dns-prefetch' href='//s.w.org' />
		<script type="text/javascript">
			window._wpemojiSettings = {"baseUrl":"https:\/\/s.w.org\/images\/core\/emoji\/2.4\/72x72\/","ext":".png","svgUrl":"https:\/\/s.w.org\/images\/core\/emoji\/2.4\/svg\/","svgExt":".svg","source":{"concatemoji":"https:\/\/www.hack520.com\/wp-includes\/js\/wp-emoji-release.min.js?ver=4.9.4"}};
			!function(a,b,c){function d(a,b){var c=String.fromCharCode;l.clearRect(0,0,k.width,k.height),l.fillText(c.apply(this,a),0,0);var d=k.toDataURL();l.clearRect(0,0,k.width,k.height),l.fillText(c.apply(this,b),0,0);var e=k.toDataURL();return d===e}function e(a){var b;if(!l||!l.fillText)return!1;switch(l.textBaseline="top",l.font="600 32px Arial",a){case"flag":return!(b=d([55356,56826,55356,56819],[55356,56826,8203,55356,56819]))&&(b=d([55356,57332,56128,56423,56128,56418,56128,56421,56128,56430,56128,56423,56128,56447],[55356,57332,8203,56128,56423,8203,56128,56418,8203,56128,56421,8203,56128,56430,8203,56128,56423,8203,56128,56447]),!b);case"emoji":return b=d([55357,56692,8205,9792,65039],[55357,56692,8203,9792,65039]),!b}return!1}function f(a){var c=b.createElement("script");c.src=a,c.defer=c.type="text/javascript",b.getElementsByTagName("head")[0].appendChild(c)}var g,h,i,j,k=b.createElement("canvas"),l=k.getContext&&k.getContext("2d");for(j=Array("flag","emoji"),c.supports={everything:!0,everythingExceptFlag:!0},i=0;i<j.length;i++)c.supports[j[i]]=e(j[i]),c.supports.everything=c.supports.everything&&c.supports[j[i]],"flag"!==j[i]&&(c.supports.everythingExceptFlag=c.supports.everythingExceptFlag&&c.supports[j[i]]);c.supports.everythingExceptFlag=c.supports.everythingExceptFlag&&!c.supports.flag,c.DOMReady=!1,c.readyCallback=function(){c.DOMReady=!0},c.supports.everything||(h=function(){c.readyCallback()},b.addEventListener?(b.addEventListener("DOMContentLoaded",h,!1),a.addEventListener("load",h,!1)):(a.attachEvent("onload",h),b.attachEvent("onreadystatechange",function(){"complete"===b.readyState&&c.readyCallback()})),g=c.source||{},g.concatemoji?f(g.concatemoji):g.wpemoji&&g.twemoji&&(f(g.twemoji),f(g.wpemoji)))}(window,document,window._wpemojiSettings);
		</script>
		<style type="text/css">
img.wp-smiley,
img.emoji {
	display: inline !important;
	border: none !important;
	box-shadow: none !important;
	height: 1em !important;
	width: 1em !important;
	margin: 0 .07em !important;
	vertical-align: -0.1em !important;
	background: none !important;
	padding: 0 !important;
}
</style>

　　方法很简单，在 functions.php 文件中植入以下代码：

/**移除window._wpemojiSettings**/
remove_action( 'admin_print_scripts', 'print_emoji_detection_script');
remove_action( 'admin_print_styles', 'print_emoji_styles');
remove_action( 'wp_head', 'print_emoji_detection_script', 7);
remove_action( 'wp_print_styles', 'print_emoji_styles');
remove_action( 'embed_head','print_emoji_detection_script');
remove_filter( 'the_content_feed', 'wp_staticize_emoji');
remove_filter( 'comment_text_rss', 'wp_staticize_emoji');
remove_filter( 'wp_mail', 'wp_staticize_emoji_for_email');

　　这样一来，再打开首页源代码，发现以上的 window._wpemojiSettings 表情代码都已经清空了，但是这句话还在：

<link rel='dns-prefetch' href='//s.w.org' />

　　这是一句 DNS 预读取代码，s.w.org 是 WordPress 官网的，关于此项请移步至：DNS Prefetch 预读取到底是什么意思？如何正确使用？

　　同样的，在 functions.php 文件中加入以下代码即可去除 DNS Prefetch：

remove_action( 'wp_head', 'wp_resource_hints', 2 );

　　听说下面的代码兼容性更好，反正我用上面的也搞定了。

function remove_dns_prefetch( $hints, $relation_type ) {
if ( 'dns-prefetch' === $relation_type ) {
return array_diff( wp_dependencies_unique_hosts(), $hints );
}
return $hints;
}
add_filter( 'wp_resource_hints', 'remove_dns_prefetch', 10, 2 );