javascript - 如何滚动查看数组中的特定项目
问题描述
我有一个组件可以在提交评论后滚动查看。
const commentSubmit = (e: any, id: number) => {
......
divRef.current.scrollIntoView({ behavior: "smooth" });
};
它滚动到<div ref={divRef]></div>最新评论底部的评论。问题是，如果我发布新帖子，它将滚动到错误的 div 元素。所以它只是在最底部滚动。我如何告诉 ref 根据评论所属的帖子滚动到特定元素？
{post.Comments.length > 0 ? (
<Fragment>
<Typography style={{ padding: "10px 0px", margin: "20px 0px" }}>Commments</Typography>
// ignore this divRef in comment list its not being called in the comment list.
<CommentList ref={divRef} user={currentUser} deleteComment={props.deleteComment} userId={post.userId} postId={post.id} comments={post.Comments} {...props} />
{/* if show more hide show more button and show show less comments button */}
</Fragment>
) : (
<Grid item={true} sm={12} lg={12} style={{ padding: "30px 0px" }}>
<Typography>No Commments Yet</Typography>
</Grid>
)}
<div ref={divRef}></div>
postItemContainer.tsx
import React, { Fragment, useState, useCallback, useRef } from "react";
import Avatar from "@material-ui/core/Avatar";
import Button from "@material-ui/core/Button";
import Grid from "@material-ui/core/Grid";
import Paper from "@material-ui/core/Paper";
import Typography from "@material-ui/core/Typography";
import DeleteOutlineOutlinedIcon from "@material-ui/icons/DeleteOutlineOutlined";
import FavoriteIcon from "@material-ui/icons/Favorite";
import FavoriteBorderIcon from "@material-ui/icons/FavoriteBorder";
import moment from "moment";
import { toast, ToastContainer } from "react-toastify";
import OurLink from "../../../common/OurLink";
import CommentForm from "../comment/CommentForm";
import CommentList from "../commentList/CommentList";
import OurModal from "../../../common/OurModal";
import "react-toastify/dist/ReactToastify.css";
function PostItemContainer(props: any) {
const [openModal, setOpenModal] = useState(false);
const [openForm, setOpenForm] = useState(false);
const [comment_body, setCommentBody] = useState("");
const [gifUrl, setGifUrl] = useState("");
const divRef = React.useRef<any>();
const writeComment = () => {
// this is the same as this.setState({ openForm: !this.state.open })
setOpenForm(!openForm);
};
const commentChange = (comment) => {
setGifUrl("");
setCommentBody(comment);
};
const selectGif = (e) => {
setGifUrl(e.images.downsized_large.url);
setCommentBody("");
// you wont be able to add text comment with a gif, it will look weird :(
};
const handleClickOpen = () => {
setOpenModal(true);
};
const handleCloseModal = () => {
setOpenModal(false);
};
const commentSubmit = (e: any, id: number) => {
e.preventDefault();
const formData = {
comment_body,
id,
gifUrl,
};
props.postComment(formData);
setCommentBody("");
setOpenForm(false);
console.log(divRef);
divRef.current.scrollIntoView({ behavior: "smooth" });
};
const { post, currentUser, getNotifications } = props;
console.log(divRef);
return (
<Fragment>
{getNotifications && <ToastContainer autoClose={1000} position={toast.POSITION.BOTTOM_RIGHT} />}
<Grid item={true} sm={12} md={12} style={{ margin: "20px 0px" }}>
<Paper style={{ padding: "20px" }}>
<Typography variant="h5" align="left">
<OurLink
style={{ fontSize: "16px" }}
to={{
pathname: `/post/${post.id}`,
state: { post },
}}
title={post.title}
/>
</Typography>
<Grid item={true} sm={12} md={12} style={{ padding: "30px 0px" }}>
<Typography align="left">{post.postContent.slice(0, 50)}</Typography>
</Grid>
<Avatar
style={{
display: "inline-block",
margin: "-10px -20px",
padding: "0px 30px 0px 20px",
}}
sizes="small"
src={post.author.gravatar}
/>
<Typography display="inline" variant="subtitle1" align="left">
<OurLink
to={{
pathname: `/profile/${post.author.username}`,
state: { post },
}}
title={post.author.username}
/>
</Typography>
<Typography align="right">Likes: {post.likeCounts}</Typography>
<Grid container={true} spacing={1} style={{ padding: "20px 0px" }}>
<Grid item={true} sm={10} lg={10} md={10} style={{ padding: "0px 0px" }}>
<Typography align="left">
{currentUser && currentUser.user && post.userId === currentUser.user.id ? (
<span style={{ cursor: "pointer" }} onClick={() => props.deletePost(post.id, post.userId)}>
<DeleteOutlineOutlinedIcon style={{ margin: "-5px 0px" }} color="primary" /> <span>Delete</span>
</span>
) : null}
</Typography>
</Grid>
<Grid item={true} sm={2} lg={2} style={{ padding: "0px 15px" }}>
<Typography align="right">
{Object.entries(currentUser).length === 0 ? (
<Fragment>
<span onClick={handleClickOpen}>
<FavoriteBorderIcon style={{ color: "red", cursor: "pointer" }} />
</span>
{openModal ? <OurModal open={openModal} handleClose={handleCloseModal} /> : null}
</Fragment>
) : (
<Fragment>
{post.likedByMe === true ? (
<span style={{ cursor: "pointer" }} onClick={() => props.dislikePost(post.id)}>
<FavoriteIcon style={{ color: "red" }} />
</span>
) : (
<span onClick={() => props.likePost(post.id)}>
<FavoriteBorderIcon style={{ color: "red", cursor: "pointer" }} />
</span>
)}
</Fragment>
)}
</Typography>
</Grid>
</Grid>
<Typography variant="h6" align="left">
{moment(post.createdAt).calendar()}
</Typography>
<Grid item={true} sm={12} lg={12} style={{ paddingTop: "40px" }}>
{Object.entries(currentUser).length === 0 ? (
<Fragment>
<Button onClick={handleClickOpen} variant="outlined" component="span" color="primary">
{"Write A Comment"}
</Button>
{openModal ? <OurModal open={openModal} handleClose={handleCloseModal} /> : null}
</Fragment>
) : (
<Fragment>
<Button onClick={writeComment} variant="outlined" component="span" color="primary">
{openForm ? "Close" : "Write A Comment"}
</Button>
</Fragment>
)}
{openForm ? (
<CommentForm
commentChange={(e: any) => commentChange(e.target.value)}
comment_body={comment_body}
onSubmit={(e) => commentSubmit(e, post.id)}
gifUrl={selectGif}
isGif={gifUrl}
/>
) : null}
{post.Comments.length > 0 ? (
<Fragment>
<Typography style={{ padding: "10px 0px", margin: "20px 0px" }}>Commments</Typography>
<CommentList ref={divRef} user={currentUser} deleteComment={props.deleteComment} userId={post.userId} postId={post.id} comments={post.Comments} {...props} />
{/* if show more hide show more button and show show less comments button */}
</Fragment>
) : (
<Grid item={true} sm={12} lg={12} style={{ padding: "30px 0px" }}>
<Typography>No Commments Yet</Typography>
</Grid>
)}
<div ref={divRef}></div>
</Grid>
</Paper>
</Grid>
</Fragment>
);
}
export default PostItemContainer
CommentList.tsx（以防万一）评论是如何映射和迭代的
import React, { Fragment, useState } from "react";
import Grid from "@material-ui/core/Grid";
import OurSecondaryButton from "../../../common/OurSecondaryButton";
import CommentListContainer from "../commentListContainer/commentListContainer";
function CommentList(props: any) {
const [showMore, setShowMore] = useState<Number>(2);
const [openModal, setOpenModal] = useState(false);
const [showLessFlag, setShowLessFlag] = useState<Boolean>(false);
const the_comments = props.comments.length;
const inc = showMore as any;
const min = Math.min(2, the_comments - inc);
const showComments = (e) => {
e.preventDefault();
if (inc + 2 && inc <= the_comments) {
setShowMore(inc + 2);
setShowLessFlag(true);
} else {
setShowMore(the_comments);
}
};
const handleClickOpen = () => {
setOpenModal(true);
};
const handleCloseModal = () => {
setOpenModal(false);
};
const showLessComments = (e) => {
e.preventDefault();
setShowMore(2);
setShowLessFlag(false);
};
const isBold = (comment) => {
return comment.userId === props.userId ? 800 : 400;
};
// show comments by recent, and have the latest comment at the bottom, with the previous one just before it.
const filterComments = props.comments
.slice(0)
.sort((a, b) => {
const date1 = new Date(a.createdAt) as any;
const date2 = new Date(b.createdAt) as any;
return date2 - date1;
})
.slice(0, inc)
.reverse();
const showMoreComments = () => {
return filterComments.map((comment, i) => (
<div key={i}>
<CommentListContainer comment={comment} openModal={openModal} handleCloseModal={handleCloseModal} isBold={isBold} handleClickOpen={handleClickOpen} {...props} />
</div>
));
};
return (
<Grid>
<Fragment>
<div style={{ margin: "30px 0px" }}>
{props.comments.length > 2 ? (
<Fragment>
{min !== -1 && min !== -2 ? (
<Fragment>
{min !== 0 ? (
<OurSecondaryButton onClick={(e) => showComments(e)} component="span" color="secondary">
View {min !== -1 && min !== -2 ? min : 0} More Comments
</OurSecondaryButton>
) : (
<OurSecondaryButton onClick={(e) => showLessComments(e)} component="span" color="secondary">
Show Less Comments
</OurSecondaryButton>
)}
</Fragment>
) : (
<OurSecondaryButton onClick={(e) => showLessComments(e)} component="span" color="secondary">
Show Less Comments
</OurSecondaryButton>
)}
</Fragment>
) : null}
</div>
</Fragment>
{showLessFlag === true ? (
// will show most recent comments below
showMoreComments()
) : (
<Fragment>
{/* filter based on first comment */}
{filterComments.map((comment, i) => (
<div key={i}>
<CommentListContainer comment={comment} openModal={openModal} handleCloseModal={handleCloseModal} isBold={isBold} handleClickOpen={handleClickOpen} {...props} />
</div>
))}
</Fragment>
)}
</Grid>
);
}
// prevents un-necesary re renders
export default React.memo(CommentList);
解决方案
这个问题似乎很复杂，但我把它复杂化了。
我要做的是添加这个
setTimeout(() => {
divRef.current.scrollIntoView({ behavior: "smooth", block: "center", inline: "nearest" });
}, 1500);
在该commentSubmit方法中，这将滚动到最近的评论。
const commentSubmit = (e: any, id: number) => {
e.preventDefault();
const formData = {
comment_body,
id,
gifUrl,
};
props.postComment(formData);
setCommentBody("");
setOpenForm(false);
console.log(divRef);
// divRef.current.scrollIntoView({ behavior: "smooth" });
// my attempt to scroll to the lastest comment.
setTimeout(() => {
divRef.current.scrollIntoView({ behavior: "smooth", block: "center", inline: "nearest" });
}, 1500);
}
并对代码进行一些调整，如果没有评论，divRef在添加评论时会抛出错误，因为它正在寻找评论但没有任何评论，所以如果评论少于1我们会这样做或 2. 在我的情况下，我使用 2 原因我最初显示 2 条评论，我有一个过滤器，显示更多评论，显示更少。
{post.Comments.length === 0 ? <div ref={divRef}></div> : null}
其余代码
{post.Comments.length === 0 ? <div ref={divRef}></div> : null}
{post.Comments.length > 0 ? (
<Fragment>
<Typography style={{ padding: "10px 0px", margin: "20px 0px" }}>Commments</Typography>
<CommentList ref={divRef} user={currentUser} deleteComment={props.deleteComment} userId={post.userId} postId={post.id} comments={post.Comments} {...props} />
{/* if show more hide show more button and show show less comments button */}
</Fragment>
) : (
<Grid item={true} sm={12} lg={12} style={{ padding: "30px 0px" }}>
<Typography>No Commments Yet</Typography>
</Grid>
)}
{post.Comments.length < 2 ? <div ref={divRef}></div> : null}
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