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HomeWeb Front-endJS TutorialConflict problem and solution of $ symbol in jQuery

在jQuery中,$是jQuery的别名,为了书写方便,我们更习惯用$('#id')这一类的方式来书写代码。当同一页面引用了jQuery多个版本或者jQuery与某些其他js库产生冲突,控制台就会报错。

同一个页面多个版本冲突解决办法

你可能会问,为什么在一个页面上会引用多个版本的jQuery,只引用一个不就好了吗?

答案是:不行。一般要用到两个(或以上)版本的jQuery库的原因是:现有的网站已经用了旧版本的jQuery以及相关插件,直接将jQuery升级到新版本会导致这些基于旧版本jQuery的插件不能工作,除非你能把这些插件全部升级,或者等各个插件的作者发布支持新版本jQuery的插件版本。  

解决办法:使用jQuery.noConflict([extreme])方法。

比如我引用的是jquery-1.11.0.js和jquery-1.5.0.js。

<script src="jquery-1.5.0.js"></script>
<script src="jquery-1.11.0.js"></script>
<script>
console.log($.fn.jquery); //&#39;1.11.0&#39;
var $jq = jQuery.noConflict(true);
console.log($.fn.jquery); //&#39;1.5.0&#39;
</script>

   


可以看到jQuery.noConflict将变量 $ 的控制权让渡给了1.5.0版本的jQuery库。而要使用1.11.0的版本则要用 $jq() 代替。 

但是引入了两个版本的jQuery后,代码很乱,导致别人难以理解甚至误删了一些重要代码怎么办?

改进的方法是:

先直接引用新版的jQuery库。

<script src="jquery-1.11.0.js"></script>
<script src="myJS.js"></script>

   


把我们写的脚本myJS.js中的主体内容写在立即调用函数里头,引用的是新的版本的jQuery。

//myJS.js
(function() {
//myJS.js的代码,引用的是v1.11.0
})();

   


再写一个立即调用函数,把旧版本的jQuery代码嵌进去(压缩代码只有几行)。然后在里面写代码,此时变量$所引用的前面嵌进去的jQuery

//myJS.js
(function () {
//...此处省略/jquery1.5.0
//jquery1.5.0的压缩代码
  var $ = jQuery.noConflict(true);
//此处开始写的$()所引用的是jquery1.5.0
})();

   


Ps:需要检查jQuery的协议是否允许我们把jQuery源码直接嵌入我们自己的JavaScript代码

2. 同一页面jQuery和其他js库冲突解决方法

①依然可以使用jQuery.noConflict将变量$的控制权让渡给其他js库。

如果jQuery在其他js库前,不需要使用noConflict。 

<!-- 引入 jquery库 -->
<script src="jquery-1.11.0.js"></script>
<script type="text/javascript">
var $jq = $;
console.log($.fn.jquery); //&#39;1.11.0&#39;
</script>
<!-- 引入 其他库-->
<script type="text/javascript">
$ = {
fn:{
jquery:"otherJS"
}
};
</script>
<script type="text/javascript">
console.log($.fn.jquery); //otherJS
console.log($jq.fn.jquery); //&#39;1.11.0&#39;
</script>

   


如果在其他js库之后,用noConflict让渡。

<!-- 引入 其他库-->
<script type="text/javascript">
$ = {
fn:{
jquery:"otherJS"
}
};
</script>
<!-- 引入 jquery库 -->
<script src="jquery-1.11.0.js"></script>
<script type="text/javascript">
console.log($.fn.jquery); //&#39;1.11.0&#39;
var $180 = $.noConflict(); //解除冲突
console.log($.fn.jquery); //otherJS
console.log($jq.fn.jquery); //&#39;1.11.0&#39;
</script>

   


它的缺点是:在接下来的js代码中只要引用到jQuery就必须把$换成$jq。

②ready函数是jquery的入口函数

可以将

$(document).ready(function() {...})

   


替换成:

jQuery(document).ready(function($) {...})

   


它的缺点是:只对ready嵌套内的代码有效,如果ready函数外还有一些子函数,对嵌套外的代码是无效的。

③把$作为参数传进去

(function($) {
//你的js代码
})(jQuery);

   


或者

jQuery(function($){
//你的js代码
}

   


你的js代码可以包括上面说到的ready函数和子函数。在用jQuery写公共组件的时候,使用这种方式既能避免$冲突,又无需要求使用公共组件的人修改自己的代码。

以上就是jQuery中 $ 符号的冲突问题及解决方案的内容,更多相关内容请关注PHP中文网(www.php.cn)!


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