When you are working with Spfx you may choose @pnp/sp library as they provides a fluent API to make building your REST queries intuitive and supports batching and caching. It is very easy to use. You can find the examples here.
I have used the below snippet to get items from the list:
import pnp from "sp-pnp-js";
pnp.sp.web.lists.getByTitle("Task").select("Title", "ID").items.get().then((items: any[]) =>
this.setState({
listItems: items
)};
});
After building my SPFX webpart, when I deployed in classic page, it worked as expected. But when I added the same webpart in modern page, I got the following error.
GET https://mysite.sharepoint.com/SitePages/_api/web 404 (Not Found)
The URL contains /SitePages that shouldn't be included.
This issue occurs as the pnp js api didn’t get the SharePoint context. So this is how I fixed the issue:
In the props file, add the webpartcontext prop:
import { WebPartContext } from "@microsoft/sp-webpart-base";
export interface IMyListTrainingMasterProps {
description: string;
context:WebPartContext;
}
In the webpart.ts file add the newly created prop and initialize it this.context to get the SharePoint context:
public render(): void {
const element: React.ReactElement<IMyListTrainingMasterProps >= React.createElement(
MyListTrainingMaster,
{
description: this.properties.description,
context: this.context
}
);
Now the final step. In your component (.tsx file), get the context of the web from the context prop which we created as below:
let web = new Web(this.props.context.pageContext.web.absoluteUrl);
web.lists.getByTitle("Task").select("Title", "ID").items.get().then((items: any[]) => {
this.setState({
listItems: items
});
}
});