playwright/docs/navigations.md
Arjun Attam 7444de4b73
docs: update navigation and loading page (#3655)
* docs: update navigation and loading doc

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2020-08-27 17:47:23 -07:00

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# Navigations
Playwright can navigate to URLs and handle navigations caused by page interactions. This guide covers common scenarios to wait for page navigations and loading to complete.
<!-- GEN:toc-top-level -->
- [Navigation lifecycle](#navigation-lifecycle)
- [Scenarios initiated by browser UI](#scenarios-initiated-by-browser-ui)
- [Scenarios initiated by page interaction](#scenarios-initiated-by-page-interaction)
- [Advanced patterns](#advanced-patterns)
<!-- GEN:stop -->
## Navigation lifecycle
Playwright splits the process of showing a new document in a page into **navigation** and **loading**.
**Navigations** can be initiated by changing the page URL or by interacting with the page (e.g., clicking a link). Navigation ends when response headers have been parsed and session history is updated. The navigation intent may be canceled, for example, on hitting an unresolved DNS address or transformed into a file download. Only after the navigation succeeds, page starts **loading** the document.
**Loading** covers getting the remaining response body over the network, parsing, executing the scripts and firing load events:
- [`page.url()`](api.md#pageurl) is set to the new url
- document content is loaded over network and parsed
- [`domcontentloaded`](api.md#event-domcontentloaded) event is fired
- page executes some scripts and loads resources like stylesheets and images
- [`load`](api.md#event-load) event is fired
- page executes dynamically loaded scripts
- `networkidle` is fired when no new network requests are made for 500 ms
## Scenarios initiated by browser UI
Navigations can be initiated by changing the URL bar, reloading the page or going back or forward in session history.
### Auto-wait
Navigating to a URL auto-waits for the page to fire the `load` event. If the page does a client-side redirect before `load`, `page.goto` will auto-wait for the redirected page to fire the `load` event.
```js
// Navigate the page
await page.goto('https://example.com');
```
### Custom wait
Override the default behavior to wait until a specific event, like `networkidle`.
```js
// Navigate and wait until network is idle
await page.goto('https://example.com', { waitUntil: 'networkidle' });
```
### Wait for element
In lazy-loaded pages, it can be useful to wait until an element is visible with [`page.waitForSelector`](./api.md#pagewaitforselectorselector-options). Alternatively, page interactions like [`page.click`](./api.md#pageclickselector-options) auto-wait for elements.
```js
// Navigate and wait for element
await page.goto('https://example.com');
await page.waitForSelector('text=Example Domain');
// Navigate and click element
// Click will auto-wait for the element
await page.goto('https://example.com');
await page.click('text=Example Domain');
```
#### API reference
- [`page.goto(url[, options])`](./api.md#pagegotourl-options)
- [`page.reload([options])`](./api.md#pagereloadoptions)
- [`page.goBack([options])`](./api.md#pagegobackoptions)
- [`page.goForward([options])`](./api.md#pagegoforwardoptions)
## Scenarios initiated by page interaction
In the scenarios below, `page.click` initiates a navigation and then waits for the navigation to complete.
### Auto-wait
By default, `page.click` will wait for the navigation step to complete. This can be combined with a page interaction on the navigated page which would auto-wait for an element.
```js
// Click will auto-wait for navigation to complete
await page.click('text=Login');
// Fill will auto-wait for element on navigated page
await page.fill('#username', 'John Doe');
```
### Custom wait
`page.click` can be combined with [`page.waitForLoadState`](./api.md#pagewaitforloadstatestate-options) to wait for a loading event.
```js
await page.click('button'); // Click triggers navigation
await page.waitForLoadState('networkidle'); // This resolves after 'networkidle'
```
### Wait for element
In lazy-loaded pages, it can be useful to wait until an element is visible with [`page.waitForSelector`](./api.md#pagewaitforselectorselector-options). Alternatively, page interactions like [`page.click`](./api.md#pageclickselector-options) auto-wait for elements.
```js
// Click triggers navigation
await page.click('text=Login');
// Click will auto-wait for the element
await page.waitForSelector('#username', 'John Doe');
// Click triggers navigation
await page.click('text=Login');
// Fill will auto-wait for element
await page.fill('#username', 'John Doe');
```
### Asynchronous navigation
Clicking an element could trigger asychronous processing before initiating the navigation. In these cases, it is recommended to explicitly call [`page.waitForNavigation`](api.md#pagewaitfornavigationoptions). For example:
* Navigation is triggered from a `setTimeout`
* Page waits for network requests before navigation
```js
await Promise.all([
page.click('a'), // Triggers a navigation after a timeout
page.waitForNavigation(), // Waits for the next navigation
]);
```
The `Promise.all` pattern prevents a race condition between `page.click` and `page.waitForNavigation` when navigation happens quickly.
### Multiple navigations
Clicking an element could trigger multiple navigations. In these cases, it is recommended to explicitly [`page.waitForNavigation`](api.md#pagewaitfornavigationoptions) to a specific url. For example:
* Client-side redirects issued after the `load` event
* Multiple pushes to history state
```js
await Promise.all([
page.waitForNavigation({ url: '**/login' }),
page.click('a'), // Triggers a navigation with a script redirect
]);
```
The `Promise.all` pattern prevents a race condition between `page.click` and `page.waitForNavigation` when navigation happens quickly.
### Loading a popup
When popup is opened, explicitly calling [`page.waitForLoadState`](api.md#pagewaitforloadstatestate-options) ensures that popup is loaded to the desired state.
```js
const [ popup ] = await Promise.all([
page.waitForEvent('popup'),
page.click('a[target="_blank"]'), // Opens popup
]);
await popup.waitForLoadState('load');
```
#### API reference
- [`page.click(selector[, options])`](./api.md#pageclickselector-options)
- [`page.waitForLoadState([state[, options]])`](./api.md#pagewaitforloadstatestate-options)
- [`page.waitForSelector(selector[, options])`](./api.md#pagewaitforselectorselector-options)
- [`page.waitForNavigation([options])`](./api.md#pagewaitfornavigationoptions)
- [`page.waitForFunction(pageFunction[, arg, options])`](./api.md#pagewaitforfunctionpagefunction-arg-options)
## Advanced patterns
For pages that have complicated loading patterns, [`page.waitForFunction`](./api.md#pagewaitforfunctionpagefunction-arg-options) is a powerful and extensible approach to define a custom wait criteria.
```js
await page.goto('http://example.com');
await page.waitForFunction(() => window.amILoadedYet());
// Ready to take a screenshot, according to the page itself.
await page.screenshot();
```
#### API reference
- [`page.waitForFunction(pageFunction[, arg, options])`](./api.md#pagewaitforfunctionpagefunction-arg-options)