feat: P selectors (#10038)
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docs/guides/query-selectors-legacy.md
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docs/guides/query-selectors-legacy.md
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# Query Selectors (legacy)
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Queries are the primary mechanism for interacting with the DOM on your site. For example, a typical workflow goes like:
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```ts
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// Import puppeteer
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import puppeteer from 'puppeteer';
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(async () => {
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// Launch the browser
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const browser = await puppeteer.launch();
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// Create a page
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const page = await browser.newPage();
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// Go to your site
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await page.goto('YOUR_SITE');
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// Query for an element handle.
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const element = await page.waitForSelector('div > .class-name');
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// Do something with element...
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await element.click(); // Just an example.
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// Dispose of handle
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await element.dispose();
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// Close browser.
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await browser.close();
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})();
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```
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## CSS
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CSS selectors follow the CSS spec of the browser being automated. We provide some basic type deduction for CSS selectors (such as `HTMLInputElement` for `input`), but any selector that contains no type information (such as `.class-name`) will need to be coerced manually using TypeScript's `as` coercion mechanism.
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### Example
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```ts
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// Automatic
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const element = await page.waitForSelector('div > input');
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// Manual
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const element = (await page.waitForSelector(
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'div > .class-name-for-input'
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)) as HTMLInputElement;
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```
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## Built-in selectors
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Built-in selectors are Puppeteer's own class of selectors for doing things CSS cannot. Every built-in selector starts with a prefix `.../` to assist Puppeteer in distinguishing between CSS selectors and a built-in.
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### Text selectors (`text/`)
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Text selectors will select "minimal" elements containing the given text, even within (open) shadow roots. Here, "minimum" means the deepest elements that contain a given text, but not their parents (which technically will also contain the given text).
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#### Example
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```ts
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// Note we usually need type coercion since the type cannot be deduced, but for text selectors, `instanceof` checks may be better for runtime validation.
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const element = await page.waitForSelector('text/My name is Jun');
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```
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### XPath selectors (`xpath/`)
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XPath selectors will use the browser's native [`Document.evaluate`](https://developer.mozilla.org/en-US/docs/Web/API/Document/evaluate) to query for elements.
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#### Example
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```ts
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// There is not type deduction for XPaths.
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const node = await page.waitForSelector('xpath/h2');
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```
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### ARIA selectors (`aria/`)
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ARIA selectors can be used to find elements with a given ARIA label. These labels are computed using Chrome's internal representation.
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#### Example
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```ts
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const node = await page.waitForSelector('aria/Button name');
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```
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### Pierce selectors (`pierce/`)
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Pierce selectors will run the `querySelector*` API on the document and all shadow roots to find an element.
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:::danger
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Selectors will **not** _partially_ pierce through shadow roots. See the examples below.
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:::
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#### Example
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Suppose the HTML is
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```html
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<div>
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<custom-element>
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<div></div>
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</custom-element>
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</div>
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```
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Then
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```ts
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// This will be two elements because of the outer and inner div.
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expect((await page.$$('pierce/div')).length).toBe(2);
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// Partial piercing doesn't work.
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expect((await page.$$('pierce/div div')).length).toBe(0);
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```
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## Custom selectors
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Puppeteer provides users the ability to add their own query selectors to Puppeteer using [Puppeteer.registerCustomQueryHandler](../api/puppeteer.registercustomqueryhandler.md). This is useful for creating custom selectors based on framework objects or other vendor-specific objects.
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@ -30,89 +30,107 @@ import puppeteer from 'puppeteer';
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})();
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```
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## CSS
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## `P` Selectors
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CSS selectors follow the CSS spec of the browser being automated. We provide some basic type deduction for CSS selectors (such as `HTMLInputElement` for `input`), but any selector that contains no type information (such as `.class-name`) will need to be coerced manually using TypeScript's `as` coercion mechanism.
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Puppeteer uses a superset of the CSS selector syntax for querying. We call this syntax _P selectors_ and it's supercharged with extra capabilities such as deep combinators and text selection.
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### Example
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:::caution
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```ts
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// Automatic
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const element = await page.waitForSelector('div > input');
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// Manual
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const element = (await page.waitForSelector(
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'div > .class-name-for-input'
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)) as HTMLInputElement;
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```
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Although P selectors look like real CSS selectors (we intentionally designed it this way), they should not be used for actually CSS styling. They are designed only for Puppeteer.
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## Built-in selectors
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:::
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Built-in selectors are Puppeteer's own class of selectors for doing things CSS cannot. Every built-in selector starts with a prefix `.../` to assist Puppeteer in distinguishing between CSS selectors and a built-in.
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:::note
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### Text selectors (`text/`)
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P selectors only work on the first "depth" of selectors; for example, `:is(div >>> a)` will not work.
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Text selectors will select "minimal" elements containing the given text, even within (open) shadow roots. Here, "minimum" means the deepest elements that contain a given text, but not their parents (which technically will also contain the given text).
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:::
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#### Example
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### `>>>` and `>>>>` combinators
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```ts
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// Note we usually need type coercion since the type cannot be deduced, but for text selectors, `instanceof` checks may be better for runtime validation.
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const element = await page.waitForSelector('text/My name is Jun');
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```
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The `>>>` and `>>>>` are called _deep descendent_ and _deep_ combinators respectively. Both combinators have the effect of going into shadow hosts with `>>>` going into every shadow host under a node and `>>>>` going into the immediate one (if the node is a shadow host; otherwise, it's a no-op).
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### XPath selectors (`xpath/`)
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:::note
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XPath selectors will use the browser's native [`Document.evaluate`](https://developer.mozilla.org/en-US/docs/Web/API/Document/evaluate) to query for elements.
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#### Example
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```ts
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// There is not type deduction for XPaths.
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const node = await page.waitForSelector('xpath/h2');
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```
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### ARIA selectors (`aria/`)
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ARIA selectors can be used to find elements with a given ARIA label. These labels are computed using Chrome's internal representation.
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#### Example
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```ts
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const node = await page.waitForSelector('aria/Button name');
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```
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### Pierce selectors (`pierce/`)
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Pierce selectors will run the `querySelector*` API on the document and all shadow roots to find an element.
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:::danger
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Selectors will **not** _partially_ pierce through shadow roots. See the examples below.
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A common question is when should `>>>>` be chosen over `>>>` considering the flexibility of `>>>`. A similar question can be asked about `>` and a space; choose `>` if you do not need to query all elements under a given node and a space otherwise. This answer extends to `>>>>` (`>`) and `>>>` (space) naturally.
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:::
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#### Example
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Suppose the HTML is
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Suppose we have the markup
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```html
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<div>
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<custom-element>
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<template shadowrootmode="open">
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<slot></slot>
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</template>
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<custom-element>
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<div></div>
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<template shadowrootmode="open">
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<slot></slot>
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</template>
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<custom-element>
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<template shadowrootmode="open">
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<slot></slot>
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</template>
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<h2>Light content</h2>
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</custom-element>
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</custom-element>
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</div>
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</custom-element>
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```
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Then
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Then `custom-element >>> h2` will return `h2`, but `custom-element >>>> h2` will return nothing since the inner `h2` is in a deeper shadow root.
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### `P`-elements
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`P` elements are [pseudo-elements](https://developer.mozilla.org/en-US/docs/Web/CSS/Pseudo-elements) with a `-p` vendor prefix. It allows you to enhance your selectors with Puppeteer-specific query engines such as XPath, text queries, and ARIA.
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#### Text selectors (`-p-text`)
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Text selectors will select "minimal" elements containing the given text, even within (open) shadow roots. Here, "minimum" means the deepest elements that contain a given text, but not their parents (which technically will also contain the given text).
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##### Example
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```ts
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// This will be two elements because of the outer and inner div.
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expect((await page.$$('pierce/div')).length).toBe(2);
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// Partial piercing doesn't work.
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expect((await page.$$('pierce/div div')).length).toBe(0);
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const element = await page.waitForSelector('div ::-p-text(My name is Jun)');
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// You can also use escapes.
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const element = await page.waitForSelector(
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':scope >>> ::-p-text(My name is Jun \\(pronounced like "June"\\))'
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);
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// or quotes
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const element = await page.waitForSelector(
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'div >>>> ::-p-text("My name is Jun (pronounced like \\"June\\")"):hover'
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);
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```
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## Custom selectors
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#### XPath selectors (`-p-xpath`)
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XPath selectors will use the browser's native [`Document.evaluate`](https://developer.mozilla.org/en-US/docs/Web/API/Document/evaluate) to query for elements.
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##### Example
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```ts
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const element = await page.waitForSelector('::-p-xpath(h2)');
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```
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#### ARIA selectors (`-p-aria`)
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ARIA selectors can be used to find elements with a given ARIA label. These labels are computed using Chrome's internal representation.
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##### Example
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```ts
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const node = await page.waitForSelector('::-p-aria(Submit)');
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```
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### Custom selectors
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Puppeteer provides users the ability to add their own query selectors to Puppeteer using [Puppeteer.registerCustomQueryHandler](../api/puppeteer.registercustomqueryhandler.md). This is useful for creating custom selectors based on framework objects or other vendor-specific objects.
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#### Example
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Suppose you register a custom selector called `lit`. You can use it like so:
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```ts
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const node = await page.waitForSelector('::-p-lit(LitElement)');
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```
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