useLoader#

useLoader is an Isomorphic API, usually used to make asynchronous requests. During Server-Side Rendering (SSR), the server uses useLoader to prefetch the data, which is then reused on the client side.

Usage#

import { useLoader } from '@modern-js/runtime';

Function Signature#

type LoaderFn = (context: runtimeContext) => Promise<unknow>;
type Options = {
  onSuccess: (data: Record<string, any>) => void;
  onError: (error: Error) => void;
  initialData: Record<string, any>;
  skip: boolean;
  params: Record<string, any>;
  static: boolean;
};
type ReturnData = {
  data: Record<string, any>;
  loading: boolean;
  error: Error;
  reload: (params?: Record<string, any>) => Promise<any> | undefined;
  reloading: boolean;
};

function useLoader(loaderFn: LoaderFn, options: Options): ReturnData;

Input#

• loaderFn: function for loading data, returning a Promise.
• options: optional configuration.
  • onSuccess: successful callback.
  • onError: error callback.
  • initialData: the initial data before the first execution,.
  • skip: when the value is true, the function does not execute.
  • params: when the result of the params serialization changes, the function is re-executed. params is also passed in as the second argument of the function.
  • static: when the value is true, useLoader is used for SSG.

Return Value#

• data: return data on successful execution.
• loading: indicates whether the function is in execution.
• error: error message when function execution fails.
• reload: the function can be re-executed after the call.
  • params: when the value is undefined, the last value will be reused; otherwise, the function will be re-executed with the new value.
• reloading: during the execution of the call to reload, the value of reloading is true.

Example#

function Container() {
  const { data, error, loading } = useLoader(
    async (context, params) => {
      console.log(params) // nicole
      return fetch(user);
    },
    {
      onSuccess: data => {
        console.log('I did success:(',  data);
      },
      onError: error => {
        console.log('I met error:)',  error);
      },
      initialData: { name: 'nicole', gender: 'female' },
      params: 'nicole'
    }
  );

  return ...;
}