49 lines
1.6 KiB
Plaintext
49 lines
1.6 KiB
Plaintext
<template>
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<div class="aa-backtop" :class="{ 'is-visible': visible, 'aa-no-ring': !showRing }"
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role="button" aria-label="返回顶部" @click="toTop">
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<svg viewBox="0 0 44 44" v-if="showRing">
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<circle class="aa-backtop-ring-bg" cx="22" cy="22" r="20" fill="none" stroke-width="2" />
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<circle class="aa-backtop-ring-fg" cx="22" cy="22" r="20" fill="none" stroke-width="2"
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:style="{ strokeDasharray: circumference, strokeDashoffset: offset }" />
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</svg>
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<span class="aa-backtop-arrow">↑</span>
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</div>
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</template>
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<script>
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export default {
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name: 'AaBackToTop',
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props: {
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threshold: { type: Number, default: 400 },
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showRing: { type: Boolean, default: true }
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},
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data: function () {
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return { visible: false, progress: 0, r: 20 };
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},
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computed: {
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circumference: function () { return 2 * Math.PI * this.r; },
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offset: function () { return this.circumference * (1 - this.progress); }
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},
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methods: {
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onScroll: function () {
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var st = window.pageYOffset || document.documentElement.scrollTop;
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var max = document.documentElement.scrollHeight - window.innerHeight;
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this.progress = max > 0 ? st / max : 0;
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this.visible = st > this.threshold;
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},
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toTop: function () {
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window.scrollTo({ top: 0, behavior: 'smooth' });
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}
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},
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mounted: function () {
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window.addEventListener('scroll', this.onScroll, { passive: true });
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this.onScroll();
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},
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beforeDestroy: function () {
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window.removeEventListener('scroll', this.onScroll);
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}
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};
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</script>
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<style src="./BackToTop.css"></style>
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