vue-exposure
v1.4.0
Published
基于InterfaceObserver API,当绑定元素出现在视窗内的时候执行回调
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vue-exposure
Based on the InterfaceObserver
API, the vue directive is used to bind the element and execute callback functions when the element appears in the viewport.
Quick Start
Install
npm install vue-exposure --save
Since InterfaceObserver
API compatibility is still not well supported in some lower versions of browsers, vue-exposure
released two packages: normal
and with polyfill
.
import normal package
import Exposure from 'vue-exposure'
import polyfill package
import Exposure from 'vue-exposure/dist/exposure-polyfill'
Use Plugin
By default, vue-exposure executes the callback function only when all areas of the element are displayed in the viewport.
Vue.use(Exposure)
Use in component
vue-exposure is based on the vue directive wrapper, making it easier to develop, components such as the following.
<template>
<div class="exposure-test">
<div class="top" v-exposure="handlerTop"></div>
<div class="middle" v-exposure="handlerMiddle"></div>
<div class="bottom" v-exposure="handlerBottom"></div>
</div>
</template>
<script>
export default {
name: 'ExposureText',
data() {
return {
handlerBottom: {
enter() {
console.log('bottom enter')
},
leave() {
console.log('bottom leave')
}
}
}
}
methods: {
handlerMiddle() {
alert('middle')
},
handlerTop() {
alert('top')
},
},
}
</script>
<style scoped>
.top {
background-color: red;
margin-bottom: 1000px;
}
.middle {
background-color: yellowgreen;
}
.bottom {
background-color: blue;
margin-top: 1000px;
}
</style>
Scroll through the interface, triggering the callback function when the element appears in the viewport.
handler
The handler is also the value of the instruction, similar to the value of the computed property, and is of two types: function or object.
function
The function type is the more common way of writing, and the function handler will only be triggered once if the element is exposed and the threshold
is met.
object
Handlers of object type need to have one of the enter
and leave
attributes, and the values of the enter
and leave
attributes are function types.
- enter: enter handler is triggered once if the element enters exposure and
threshold
is met - leave: leave handler is triggered once after the enter handler is triggered and the element leaves the visible area completely.
threshold
By default, exposure callbacks are not executed until the entire bound element is wrapped. If you have a need when a certain percentage of the element is exposed, the threshold can be set in the following two ways.
Global threshold
vue-exposure supports global threshold setting.
Vue.use(Exposure, {
threshold: 0.2,
})
As shown in the above code, the callback function is executed when the exposure ratio of the element reaches 0.2.
Element threshold
If you want an element to have a different exposure ratio than other elements, you can set the threshold for the element separately.
<template>
<div class="exposure-test">
<div class="top" v-exposure:[0.1]="handlerTop"></div>
<div class="middle" v-exposure:[0.5]="handlerMiddle"></div>
<div class="bottom" v-exposure:[threshold]="handlerBottom"></div>
</div>
</template>
<script>
export default {
name: 'ExposureText',
data() {
return {
threshold: 0.8,
}
},
}
</script>
The directive is parameterized using Vue's dynamic directive parameters, which must be passed as a value between [0,1]
so that the exposure is scaled to the passed value when listening to the exposure.
Note: Element threshold > Global threshold.
$resetExposure
The execution of the exposure callback is single-case, which means that when exposed once and the callback is executed, the callback function is not executed when exposed again.
In the case of a KeepAlive scenario in a Vue component, the exposure callback is not re-executed when the KeepAlive component is switched. In this case, you need to use the $resetExposure
API to reset the element state if you want to re-execute it.
deactivated() {
this.$resetExposure()
}
When this.$resetExposure()
is called without any arguments, it resets the execution state of all listener elements in the current instance. If you need to reset the execution state of just one element, you need to pass in the current element.
deactivated() {
this.$resetExposure(this.$refs.el)
}
Vue 2 + composition-api
If the project is built with Vue 2 + composition-api, useResetExposure to reset the exposure in order to follow the composition-api coding specification.
import { useResetExposure } from 'vue-exposure'
import { defineComponent, onDeactivated } from '@vue/composition-api'
export default defineComponent({
setup() {
onDeactivated(() => {
useResetExposure()
})
}
})
Caution
vue-exposure listens on elements in strict mode, and does not listen on elements whose visibility
is hidden
or whose width
is 0
or whose height
is 0
.