How to get 'Last Update Date' of a blog post in GATSBY.js - graphql

Question

Hello I'm not a dev so may the question will be easy for you guys. I used the advance starter from gatsby site. The blog is working perfect but I need to provide the LAST UPDATED time under my title. Searched for some solutions but none of them worked. Could you Provide some help?
gatsby-node.js
exports.onCreateNode = ({ node, getNode, actions }) => {
const { createNodeField } = actions;
if (node.internal.type !== 'MarkdownRemark') {
return;
}
const fileNode = getNode(node.parent);
createNodeField({
node,
name: 'modifiedTime',
value: fileNode.mtime
});
};
`````````````````````````
PostListing.jsx
class PostListing extends React.Component {
getPostList() {
const postList = [];
this.props.postEdges.forEach(postEdge => {
postList.push({
path: postEdge.node.fields.slug,
tags: postEdge.node.frontmatter.tags,
cover: postEdge.node.frontmatter.cover,
title: postEdge.node.frontmatter.title,
date: postEdge.node.fields.date,
excerpt: postEdge.node.excerpt,
timeToRead: postEdge.node.timeToRead,
modifiedTime:postEdge.node.modifiedTime
});
});
return postList;
}
render() {
const postList = this.getPostList();
return (
<div className='posts'>
{/* Your post list here. */
postList.map(post => (
<Fragment>
<div className='singlePost__date'>
<h4 style={{color:'white'}}> {post.modifiedTime}</h4>
</div>
<div className='singlePost__Title'>
<Link classname='singlePost' to={post.path} key={post.title}>
<h1 className='singlePost__title'>{post.title}</h1>
</Link>
</div>
</Fragment>
))}
</div>
);
}
}
export default PostListing;
I expect something like
TITLE
last updated : 3/2/2019

Answer 1

You can use information stored in Git to get the latest time when a file was modified.
1st approach
Track it manually, but this can be error-prone if you forget to edit the modified time. So I would recommend that as the last option if you can't get others to work.
2nd approach
You can edit your gatsby-node.js to pull information from Git like so:
const { execSync } = require("child_process")
exports.onCreateNode = ({ node, actions }) => {
// ...
if (node.internal.type === "MarkdownRemark") {
const gitAuthorTime = execSync(
`git log -1 --pretty=format:%aI ${node.fileAbsolutePath}`
).toString()
actions.createNodeField({
node,
name: "gitAuthorTime",
value: gitAuthorTime,
})
}
// ...
}
Then, in your template, you can fetch it:
query($slug: String!) {
markdownRemark(fields: { slug: { eq: $slug } }) {
# ...
fields {
gitAuthorTime
}
# ...
}
}
And, finally, use it in JSX like so:
import React from "react"
const BlogPost = (props) => {
const { gitAuthorTime } = props.data.markdownRemark.fields
render(<p>Updated at: ${gitAuthorTime}</p>)
}
export default BlogPost
3rd approach
Similar to the previous one but it uses a plugin gatsby-transformer-info. It does a similar thing as in the 2nd approach, but you need to access the modified time differently this time. Like so:
query($slug: String!) {
markdownRemark(fields: { slug: { eq: $slug } }) {
# ...
parent {
... on File {
fields {
gitLogLatestDate
}
}
}
# ...
}
}
I wrote more about this in my blog post "Add Updated At To Your Gatsby Blog" if you want to check it out.

Answer 2

Edit: The answer below is actually wrong, since File. modifiedTime is the modifiedTime of the markdown file itself & not the modifiedTime for your content. For example, if you deploy your blog on say, Netlify, then the modifiedTime of your files there will be different than in your local environment.
I think the right answer is to track it separately. If you're using a CMS like NetlifyCMS, you can create a field that automatically update the date/time on every edit.
Wherever you're querying for your markdown files, you can use the below field:
query {
allMarkdownRemark {
edges {
node {
frontmatter { /* other stuff */ }
parent {
... on File {
modifiedTime(formatString: "MM/DD/YYYY")
}
}
}
}
}
}
And access it in your via postEdge.node.parent.modifiedTime