index.tsx
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import {
defineComponent,
computed,
ref,
unref,
reactive,
onMounted,
watch,
nextTick,
CSSProperties,
} from 'vue';
import { useEventListener } from '/@/hooks/event/useEventListener';
import { convertToUnit } from '/@/components/util';
import { props as basicProps } from './props';
import { getSlot } from '/@/utils/helper/tsxHelper';
import './index.less';
const prefixCls = 'virtual-scroll';
export default defineComponent({
name: 'VirtualScroll',
props: basicProps,
setup(props, { slots }) {
const wrapElRef = ref<HTMLDivElement | null>(null);
const state = reactive({
first: 0,
last: 0,
scrollTop: 0,
});
const getBenchRef = computed(() => {
return parseInt(props.bench as string, 10);
});
const getItemHeightRef = computed(() => {
return parseInt(props.itemHeight as string, 10);
});
const getFirstToRenderRef = computed(() => {
return Math.max(0, state.first - unref(getBenchRef));
});
const getLastToRenderRef = computed(() => {
return Math.min((props.items || []).length, state.last + unref(getBenchRef));
});
const getContainerStyleRef = computed(
(): CSSProperties => {
return {
height: convertToUnit((props.items || []).length * unref(getItemHeightRef)),
};
}
);
const getWrapStyleRef = computed(
(): CSSProperties => {
const styles: Recordable<string> = {};
const height = convertToUnit(props.height);
const minHeight = convertToUnit(props.minHeight);
const minWidth = convertToUnit(props.minWidth);
const maxHeight = convertToUnit(props.maxHeight);
const maxWidth = convertToUnit(props.maxWidth);
const width = convertToUnit(props.width);
if (height) styles.height = height;
if (minHeight) styles.minHeight = minHeight;
if (minWidth) styles.minWidth = minWidth;
if (maxHeight) styles.maxHeight = maxHeight;
if (maxWidth) styles.maxWidth = maxWidth;
if (width) styles.width = width;
return styles;
}
);
watch([() => props.itemHeight, () => props.height], () => {
onScroll();
});
function getLast(first: number): number {
const wrapEl = unref(wrapElRef);
if (!wrapEl) {
return 0;
}
const height = parseInt(props.height || 0, 10) || wrapEl.clientHeight;
return first + Math.ceil(height / unref(getItemHeightRef));
}
function getFirst(): number {
return Math.floor(state.scrollTop / unref(getItemHeightRef));
}
function onScroll() {
const wrapEl = unref(wrapElRef);
if (!wrapEl) {
return;
}
state.scrollTop = wrapEl.scrollTop;
state.first = getFirst();
state.last = getLast(state.first);
}
function renderChildren() {
const { items = [] } = props;
return items.slice(unref(getFirstToRenderRef), unref(getLastToRenderRef)).map(genChild);
}
function genChild(item: any, index: number) {
index += unref(getFirstToRenderRef);
const top = convertToUnit(index * unref(getItemHeightRef));
return (
<div class={`${prefixCls}__item`} style={{ top }} key={index}>
{getSlot(slots, 'default', { index, item })}
</div>
);
}
onMounted(() => {
state.last = getLast(0);
nextTick(() => {
const wrapEl = unref(wrapElRef);
if (!wrapEl) {
return;
}
useEventListener({
el: wrapEl,
name: 'scroll',
listener: onScroll,
wait: 0,
});
});
});
return () => (
<div class={prefixCls} style={unref(getWrapStyleRef)} ref={wrapElRef}>
<div class={`${prefixCls}__container`} style={unref(getContainerStyleRef)}>
{renderChildren()}
</div>
</div>
);
},
});