---
nav:
  title: FAQ
toc: menu
---

# FAQ

## `Application died in status LOADING_SOURCE_CODE: You need to export the functional lifecycles in xxx entry`

This error thrown as qiankun could not find the exported lifecycle method from your entry js.

To solve the exception, try the following steps:

1. check you have exported the specified lifecycles, see the [doc](/guide/getting-started#1-exports-lifecycles-from-sub-app-entry)

2. check you have set the specified configuration with your bundler, see the [doc](/guide/getting-started#2-config-sub-app-bundler)

3. check your `package.json` name field is unique between sub apps.

4. Check if the entry js in the sub-app's entry HTML is the last script to load. If not, move the order to make it be the last, or manually mark the entry js as `entry` in the HTML, such as:
   ```html {2}
   <script src="/antd.js"></script>
   <script src="/appEntry.js" entry></script>
   <script src="https://www.google.com/analytics.js"></script>
   ```

If it still not works after the steps above, this is usually due to browser compatibility issues. Try to **set the webpack `output.library` of the broken sub app the same with your main app registration for your app**, such as:

Such as here is the main configuration:

```ts {4}
// main app
registerMicroApps([
  {
    name: 'brokenSubApp',
    entry: '//localhost:7100',
    container: '#yourContainer',
    activeRule: '/react',
  },
]);
```

Set the `output.library` the same with main app registration:

```js {4}
module.exports = {
  output: {
    // Keep the same with the registration in main app
    library: 'brokenSubApp',
    libraryTarget: 'umd',
    jsonpFunction: `webpackJsonp_${packageName}`,
  },
};
```

## Vue Router Error - `Uncaught TypeError: Cannot redefine property: $router`

If you pass `{ sandbox: true }` to `start()` function, `qiankun` will use `Proxy` to isolate global `window` object for sub applications. When you access `window.Vue` in sub application's code，it will check whether the `Vue` property in the proxyed `window` object. If the property does not exist, it will look it up in the global `window` object and return it.

There are three lines code in the `vue-router` as followed, and it will access `window.Vue` once the `vue-router` module is loaded. And the `window.Vue` in following code is your master application's `Vue`.

```javascript
if (inBrowser && window.Vue) {
  window.Vue.use(VueRouter)
}
```

To solve the error, choose one of the options listed below:

1. Use bundler to pack `Vue` library, instead of CDN or external module
2. Rename `Vue` to other name in master application, eg: `window.Vue2 = window.Vue; window.Vue = undefined`

## Tips on Using Vue Router

The qiankun main app activates the corresponding micro app according to the `activeRule` configuration.

### a. The main app is using Vue Router's hash mode

When the main app is in hash mode, generally, micro app is also in hash mode. In this case, the base hash path of the main app is assigned to the corresponding micro app (e.g. `#base`). At this time, if the micro app needs to make a secondary path jump in hash mode (such as `#/base1/child1`) when there is a base path, you just need to add a prefix for each route yourself.     
The base parameter in VueRouter's hash mode [does not support adding a hash path base](https://github.com/vuejs/vue-router/blob/dev/src/index.js#L55-L69).

### b. The main app is using Vue Router's history mode

When the main app is in history mode and the micro app is also in history mode, it works perfectly. And if the micro app needs to add a base path, just [set the base property](https://router.vuejs.org/api/#base) of the sub item.

When the main app is in history mode and the micro app is in hash mode, it works perfectly.

## Why dynamic imported assets missing?

Two way to solve that:

### 1. With webpack live public path config

qiankun will inject a live public path variable before your sub app bootstrap, what you need is to add this code at the top of your sub app entry js:

```js
__webpack_public_path__ = window.__INJECTED_PUBLIC_PATH_BY_QIANKUN__;
```

For more details, check the [webpack doc](https://webpack.js.org/guides/public-path/#on-the-fly).

<Alert type="info">
Runtime publicPath addresses the problem of incorrect scripts, styles, images, and other addresses for dynamically loaded in sub application.
</Alert>

### 2. With webpack static public path config

You need to set your publicPath configuration to an absolute url, and in development with webpack it might be:

```js
{
  output: {
    publicPath: `//localhost:${port}`;
  }
}
```

## Must a sub app asset support cors?

Yes it is.

Since qiankun get assets which imported by sub app via fetch, these static resources must be required to support [cors](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS).

See [Enable Nginx Cors](https://enable-cors.org/server_nginx.html).

## How to guarantee the main app stylesheet isolated with sub apps?

Qiankun will isolate stylesheet between your sub apps automatically, you can manually ensure isolation between master and child applications. Such as add a prefix to all classes in the master application, and if you are using [ant-design](https://ant.design), you can follow [this doc](https://ant.design/docs/react/customize-theme) to make it works.

## How to make sub app to run independently?

Use the builtin global variable to identify the environment which provided by qiankun master:

```js
if (!window.__POWERED_BY_QIANKUN__) {
  render();
}

export const mount = async () => render();
```

## Could I active two sub apps at the same time?

When the subapp should be active depends on your `activeRule` config, like the example below, we set `activeRule` logic the same between `reactApp` and `react15App`:

```js {2,3,7}
registerMicroApps([
  // define the activeRule by your self
  { name: 'reactApp', entry: '//localhost:7100', container, activeRule: () => window.isReactApp },
  { name: 'react15App', entry: '//localhost:7102', container, activeRule: () => window.isReactApp },
  { name: 'vue app', entry: '//localhost:7101', container, activeRule: () => window.isVueApp },
]);

start({ singular: false });
```

After setting `singular: false` in `start` method, `reactApp` and `react15App` should be active at the same time once `isReactApp` method returns `true`.

<Alert>
Notice that no more than one application that relies on router can be displayed on the page at the same time, as the browser has only one url location, if there is more than one routing apps, it will definitely result in one of them to be 404 found.
</Alert>

## How to extract the common library？

> Don’t share a runtime, even if all teams use the same framework. - [Micro Frontends](https://micro-frontends.org/)

Although sharing dependencies isn't a good idea, but if you really need it, you can external the common dependencies from sub apps and then import them in master app.

In the future qiankun will provide a smarter way to make it automatically.

## Does qiankun compatible with ie?

Yes.

However, the IE environment (browsers that do not support Proxy) can only use the single-instance pattern, where the `singular` configuration will be set `true` automatically by qiankun if IE detected.

You can find the singular usage [here](/api#startopts).

### How to polyfill IE?

If you want qiankun (or its dependent libraries, or your own application) to work properly in IE, you need to introduce the following polyfills at the portal **at least**:

<Alert type="info">
What's <a href="https://developer.mozilla.org/en-US/docs/Glossary/Polyfill" target="_blank">polyfill</a>
</Alert>

```javascript
import 'whatwg-fetch';
import 'custom-event-polyfill';
import 'core-js/stable/promise';
import 'core-js/stable/symbol';
import 'core-js/stable/string/starts-with';
import 'core-js/web/url';
```

**We recommend that you use @babel/preset-env plugin directly to polyfill IE automatically, all the instructions for @babel/preset-env you can found in [babel official document](https://babeljs.io/docs/en/babel-preset-env).**

## Error `Here is no "fetch" on the window env, you need to polyfill it`

Qiankun use `window.fetch` to get resources of the micro applications, but [some browsers does not support it](https://caniuse.com/#search=fetch), you should get the [polyfill](https://github.com/github/fetch) in the entry.

## Does qiankun support the subApp without bundler?

> Yes

The only change is that we need to declare a script tag, to export the `lifecycles`

example:

1. declare entry script

```diff
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Purehtml Example</title>
</head>
<body>
  <div>
    Purehtml Example
  </div>
</body>

+ <script src="//yourhost/entry.js" entry></script>
</html>
```

2. export lifecycles in the entry

```javascript
const render = ($) => {
  $('#purehtml-container').html("Hello, render with jQuery");
  return Promise.resolve();
}

(global => {
  global['purehtml'] = {
    bootstrap: () => {
      console.log('purehtml bootstrap');
      return Promise.resolve();
    },
    mount: () => {
      console.log('purehtml mount');
      return render($)
    },
    unmount: () => {
      console.log('purehtml unmount');
      return Promise.resolve();
    },
  };
})(window);
```

refer to the [purehtml examples](https://github.com/umijs/qiankun/tree/master/examples/purehtml)

At the same time, [the subApp must support the CORS](#must-a-sub-app-asset-support-cors)

## How to handle subapplication JSONP cross-domain errors?

qiankun will convert the dynamic script loading of the subapplication (such as JSONP) into a fetch request, so the corresponding back-end service needs to support cross-domain, otherwise it will cause an error.

In singular mode, you can use the `excludeAssetFilter` parameter to release this part of the resource request, but note that the resources released by this option will escape the sandbox, and the resulting side effects need to be handled by you.

If you use JSONP in not-singular mode, simply using `excludeAssetFilter` does not achieve good results, because each application is isolated by the sandbox; you can provide a unified JSONP tool in the main application, and the subapplication just calls the tool.