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| <template>
<div class="affix-placeholder" :style="wrapStyle">
<div :class="{ affix: affixed }" :style="styles">
<slot></slot>
</div>
</div>
</template>
<script>
export default {
props: {
offset: {
type: Number,
default: 0,
},
onAffix: {
type: Function,
default() {},
},
boundary: {
type: String,
default: "",
},
},
data() {
return {
affixed: false,
styles: {},
affixedClientHeight: 0,
wrapStyle: {},
};
},
methods: {
getScroll(w, top) {
let ret = w[`page${top ? "Y" : "X"}Offset`];
const method = `scroll${top ? "Top" : "Left"}`;
if (typeof ret !== "number") {
const d = w.document;
ret = d.documentElement[method];
if (typeof ret !== "number") {
ret = d.body[method];
}
}
return ret;
},
getOffset(element) {
const rect = element.getBoundingClientRect();
const body = document.body;
const clientTop = element.clientTop || body.clientTop || 0;
const clientLeft = element.clientLeft || body.clientLeft || 0;
const scrollTop = this.getScroll(window, true);
const scrollLeft = this.getScroll(window);
return {
top: rect.bottom + scrollTop - clientTop - this.affixedClientHeight,
left: rect.left + scrollLeft - clientLeft,
};
},
handleScroll() {
const scrollTop = this.getScroll(window, true) + this.offsets;
const elementOffset = this.getOffset(this.$el);
if (!this.affixed && scrollTop > elementOffset.top) {
this.affixed = true;
this.styles = {
top: `${this.offsets}px`,
left: `${elementOffset.left}px`,
width: `${this.$el.offsetWidth}px`,
};
this.onAffix(this.affixed);
}
if (this.boundary && scrollTop > elementOffset.top) {
const el = document.getElementById(this.boundary.slice(1));
if (el) {
const boundaryOffset = this.getOffset(el);
if (scrollTop + this.offsets > boundaryOffset.top) {
const top = scrollTop - boundaryOffset.top;
this.styles.top = `-${top}px`;
}
}
}
if (this.affixed && scrollTop < elementOffset.top) {
this.affixed = false;
this.styles = {};
this.onAffix(this.affixed);
}
if (this.affixed && this.boundary) {
const el = document.getElementById(this.boundary.slice(1));
if (el) {
const boundaryOffset = this.getOffset(el);
if (scrollTop + this.offsets <= boundaryOffset.top) {
this.styles.top = 0;
}
}
}
},
},
computed: {
offsets() {
if (this.boundary) {
return 0;
}
return this.offset;
},
},
mounted() {
this.affixedClientHeight = this.$el.children[0].clientHeight;
this.wrapStyle = { height: `${this.affixedClientHeight}px` };
window.addEventListener("scroll", this.handleScroll);
window.addEventListener("resize", this.handleScroll);
},
beforeDestroy() {
window.removeEventListener("scroll", this.handleScroll);
window.removeEventListener("resize", this.handleScroll);
},
};
</script>
<style >
.affix {
position: fixed;
}
</style>
|