1. 原生js中我们会使用document.getElementsByClassName(),document.getElementById()等获取dom元素,但在vue中,更推荐使用ref获取。
2. 不同文件的ref相互独立,即使同名也不会互相影响而导致获取错误。一个组件被多次引用后同时存在多个实例时,每个实例的ref也是互相独立的。这一点显然比getElementById()要好很多。
3. 标签的ref属性值在每一个vue文件中需要是唯一的,否则可能在获取时发生与预期不同的效果。显然使用v-for时如果单项带有ref就需要我们解决这个问题。
目录
使用ref绑定Dom元素
- 用法相当简单,我们在想获取的标签上增加属性 ref="refName" 即可。
- 例如:
<template>
<span id="myspanid" ref="mySpanRef">hello coolight</span>
</template>
获取
获取的方式很多,这里介绍其中的几种,以及提及一些document的方法和注意事项
祖传getElementById()
- 在vue中,getElementById()依然可用,但不建议,而且要注意生命周期问题
<script setup>
import { onMounted } from "vue";
let span_id = document.getElementById("myspanid");
console.log("setup: span_id = ", span_id);
onMounted(() => {
console.log("onMounted: span_id = ", span_id);
span_id = document.getElementById("myspanid");
console.log("onMounted: span_id = ", span_id);
})
</script>
<template>
<span id="myspanid" ref="mySpanRef">hello coolight</span>
</template>
- 运行结果:
- 可以看到,在setup中直接使用getElementById()是不行的,需要在onMounted(也就是已经把dom元素挂载完成后)重新调用getElementById()获取。
- 这就是vue的生命周期问题,贴一张vue官网的图,具体有关生命周期的在此不展开讲了:
ref(null)
- refName = ref(null)是常见的获取方法
- 即声明一个与在标签中ref元素值同名的变量,然后调用ref(null)即可获取到。
- 注意需要导入:import { ref } from "vue";
- 示例:
<script setup>
import { ref,onMounted, getCurrentInstance } from "vue";
let mySpanRef = ref(null);
console.log("setup: mySpanRef = ", mySpanRef);
console.log("setup: mySpanRef.value = ", mySpanRef.value);
onMounted(() => {
console.log("读取setup获取的mySpanRef:");
console.log("onMounted: mySpanRef = ", mySpanRef);
console.log("onMounted: mySpanRef.value = ", mySpanRef.value);
mySpanRef = ref(null);
console.log("读取onMounted获取的mySpanRef:");
console.log("onMounted: mySpanRef = ", mySpanRef);
console.log("onMounted: mySpanRef.value = ", mySpanRef.value);
})
</script>
<template>
<span ref="mySpanRef">hello coolight</span>
</template>
- 运行结果:
- 可以看到 ref(null) 返回的是一个 RefImpl 对象,如果想它打印结果和getElementById()一样,则需要 .value。如果我们想调用元素的操作方法等,也需要.value后再接操作方法。
- 比如:
<script setup>
import { ref, onMounted } from "vue";
const mySpanRef = ref(null);
onMounted(() => {
console.log(mySpanRef);
console.log(mySpanRef.clientWidth);
console.log(mySpanRef.value.clientWidth);
})
</script>
<template>
<span ref="mySpanRef">hello coolight</span>
</template>
- 运行结果:
- 显然,使用ref(null)获取的也会有生命周期问题,但这次仅仅是mySpanRef.value = null。
- 而且我们要注意应在setup中调用ref(null)获取,但在onMounted以后才能访问其.value,进行dom相关的函数调用操作。
- 如果在onMounted内调用ref(null)获取反而获取不到。
$refs.refName
- 这个方法则不需要变量名和ref值相同
- 注意:
- 需要在onMounted后获取
- 需要导入getCurrentInstance()
- 如果在setup直接调用了getCurrentInstance(),将导致在onMounted()中获取失败。
- 示例:
<script setup>
import { onMounted, getCurrentInstance } from "vue";
let mySpan;
onMounted(() => {
let { $refs } = (getCurrentInstance()).proxy;
mySpan = $refs.mySpanRef;
console.log("onMounted: mySpan = ", mySpan);
})
</script>
<template>
<span ref="mySpanRef">hello coolight</span>
</template>
- 运行结果:
- 如你所见,返回和getElementById()一样,我们可以直接调用dom标签的方法而不需要像ref(null)获取后.value。
$refs[refName]
- 前面我们介绍的都是需要将refName当成变量名一样写,而不能使用字符串。
- 这个方法可以传refName的字符串类型,这将大大提高我们获取的灵活度,而且它也不限制接收的变量名。
- 示例:
<script setup>
import { onMounted, getCurrentInstance } from "vue";
let mySpan;
onMounted(() => {
let { $refs } = (getCurrentInstance()).proxy;
let name = "mySpanRef";
mySpan = $refs[name];
//mySpan = $refs['mySpanRef']; //这个也是可以的
console.log("onMounted: mySpan = ", mySpan);
})
</script>
<template>
<span ref="mySpanRef">hello coolight</span>
</template>
- 运行结果:
- 其返回值同$refs.refName。
多个同名ref的解决方法
上面我们都是把ref当成id一样使用,但在v-for后产生的列表项可能遇到ref重复,下面我们聊聊如何解决这个问题
- 首先我们来看看如果ref重复,我们获取时会发生什么:
- 示例:
<script setup>
import { ref, onMounted, getCurrentInstance } from "vue";
let mySpanRef = ref(null);
onMounted(() => {
console.log("ref(null) = ", mySpanRef.value);
let { $refs } = (getCurrentInstance()).proxy;
mySpanRef = $refs.mySpanRef;
console.log("$refs.mySpanRef = ", mySpanRef);
mySpanRef = $refs['mySpanRef'];
console.log("$refs['mySpanRef'] = ", mySpanRef);
})
</script>
<template>
<div>
<span ref="mySpanRef">hello coolight</span>
<span ref="mySpanRef">hello 洛天依</span>
</div>
</template>
- 运行结果:
- 可以看到,三个方法都是得到了后一个拥有这个refName的标签
- 虽然没有报错或是警告,但已经不是预期的效果了(按平常感觉应返回一个数组)
- 解决思路:
- 我们需要改造,使得ref仍然是唯一的。
- 那么我们可以给这些同名的ref标签在refName后面再加一个id,就可以使得refName是唯一
- 显然我们需要利用第三种获取方法($refs['refName']),并用字符串拼接来生成refName
- 示例:
<script setup>
import { onMounted, getCurrentInstance } from "vue";
let arr = ['coolight', '洛天依', 'enter', 'shift', 'ctrl', 'Alt', 'ESC'];
onMounted(() => {
let { $refs } = (getCurrentInstance()).proxy;
console.log($refs['myspan0']);
console.log("for:");
for(let i = arr.length; i-- > 0;) {
console.log($refs['myspan'+ i][0]);
}
})
</script>
<template>
<div style="display:flex;flex-direction: column;">
<span v-for="(item, index) in arr"
:ref="'myspan' + index">{{index}}:{{item}}</span>
</div>
</template>
- 运行结果:
- 可以看到,这一次$refs['refName']返回的是一个包含一个span标签的数组,因此我们需要后面再加[0]访问数组内容。
其他问题
返回的是一个proxy对象
- 当返回的是proxy对象时,它的$el属性就是我们需要的标签
- 示例:
let { $refs } = (getCurrentInstance()).proxy;
let dom = $refs['myul']; //proxy对象
dom.$el; //标签内容
dom.$el.clientWidth; //通过$el即可同getElementById()获取到的标签一样操作
casino tr?c tuy?n uy tín: casino tr?c tuy?n vi?t nam – casino tr?c tuy?n vi?t nam
http://casinvietnam.com/# game c? b?c online uy tin
casino tr?c tuy?n: casino tr?c tuy?n vi?t nam – choi casino tr?c tuy?n trên di?n tho?i
casino tr?c tuy?n: casino tr?c tuy?n vi?t nam – casino online uy tín
Oh my goodness! Incredible article dude! Thank
you, However I am going through problems with your RSS.
I don’t know why I am unable to subscribe to it. Is there anyone else having similar
RSS problems? Anyone that knows the answer can you kindly respond?
Thanks!!
Hi there, constantly i used to check webpage posts here early in the daylight, for the reason that i
love to learn more and more.
PBN sites
We will create a network of private blog network sites!
Pros of our self-owned blog network:
We carry out everything SO THAT google doesn’t understand that this A privately-owned blog network!!!
1- We purchase domains from distinct registrars
2- The principal site is hosted on a VPS hosting (VPS is fast hosting)
3- Additional sites are on separate hostings
4- We assign a distinct Google profile to each site with verification in Google Search Console.
5- We develop websites on WordPress, we don’t employ plugins with aided by which malware penetrate and through which pages on your websites are created.
6- We do not duplicate templates and utilise only individual text and pictures
We never work with website design; the client, if desired, can then edit the websites to suit his wishes
casino online uy tin game c? b?c online uy tin casino tr?c tuy?n vi?t nam
Yesterday, while I was at work, my sister stole my iPad and tested
to see if it can survive a 25 foot drop, just so she can be a youtube sensation. My apple ipad is now destroyed and she has 83 views.
I know this is totally off topic but I had to share it with someone!
It’s enormous that you are getting thoughts from this piece of writing as well as from our discussion made at this time.
https://casinvietnam.shop/# choi casino tr?c tuy?n tren di?n tho?i
casino online uy tin game c? b?c online uy tin danh bai tr?c tuy?n
http://casinvietnam.com/# danh bai tr?c tuy?n
https://casinvietnam.shop/# casino online uy tin
web c? b?c online uy tín: web c? b?c online uy tín – casino tr?c tuy?n
danh bai tr?c tuy?n casino online uy tin casino online uy tin
choi casino tr?c tuy?n tren di?n tho?i casino tr?c tuy?n vi?t nam game c? b?c online uy tin
https://casinvietnam.shop/# danh bai tr?c tuy?n
http://casinvietnam.com/# game c? b?c online uy tin
I really like reading through a post that can make
men and women think. Also, thank you for permitting
me to comment!
casino online uy tín: dánh bài tr?c tuy?n – casino tr?c tuy?n vi?t nam
casino tr?c tuy?n uy tin game c? b?c online uy tin casino tr?c tuy?n vi?t nam
danh bai tr?c tuy?n web c? b?c online uy tin game c? b?c online uy tin
canadian pharmacy online no prescription: buying prescription drugs in india – non prescription canadian pharmacy
online pharmacy canada no prescription: non prescription canadian pharmacy – online pharmacy no prescriptions
buy meds online no prescription: canadian pharmacy no prescription – online pharmacy without prescription
https://edpill.top/# ed medications online
buy prescription online buy medications online without prescription online pharmacy not requiring prescription
prescription drugs canada canadian pharmacy online no prescription buy medication online no prescription
mail order prescription drugs from canada: online pharmacy without prescription – promo code for canadian pharmacy meds
https://edpill.top/# ed drugs online
http://onlinepharmacyworld.shop/# promo code for canadian pharmacy meds
https://medicationnoprescription.pro/# mexican pharmacy no prescription
low cost ed meds online: online ed prescription – online ed treatments
no prescription medicines: medications online without prescriptions – buying online prescription drugs
https://onlinepharmacyworld.shop/# canadian pharmacy no prescription needed
https://edpill.top/# buy erectile dysfunction medication
cheap erectile dysfunction pills: online ed medication – low cost ed meds online
mexican pharmacies no prescription: buy pain meds online without prescription – no prescription needed
http://edpill.top/# edmeds
http://medicationnoprescription.pro/# canada mail order prescriptions
canadian pharmacy world coupon code: canadian pharmacy no prescription – canadian pharmacy no prescription needed
online pharmacy canada no prescription online drugs without prescription medications online without prescription
canadian pharmacy without prescription online pharmacy discount code cheapest pharmacy to fill prescriptions without insurance
cheap ed meds online: edmeds – discount ed meds
canadian pharmacy no prescription: online pharmacies no prescription – canadian rx prescription drugstore
https://edpill.top/# ed meds online
http://edpill.top/# generic ed meds online
medication online without prescription: online drugstore no prescription – buying prescription drugs online without a prescription
https://medicationnoprescription.pro/# quality prescription drugs canada