playwright/docs/src/api/class-selectors.md
2021-01-07 11:46:05 -08:00

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# class: Selectors
Selectors can be used to install custom selector engines. See [Working with selectors](./selectors.md#working-with-selectors) for more
information.
## async method: Selectors.register
An example of registering selector engine that queries elements based on a tag name:
```js
const { selectors, firefox } = require('playwright'); // Or 'chromium' or 'webkit'.
(async () => {
// Must be a function that evaluates to a selector engine instance.
const createTagNameEngine = () => ({
// Returns the first element matching given selector in the root's subtree.
query(root, selector) {
return root.querySelector(selector);
},
// Returns all elements matching given selector in the root's subtree.
queryAll(root, selector) {
return Array.from(root.querySelectorAll(selector));
}
});
// Register the engine. Selectors will be prefixed with "tag=".
await selectors.register('tag', createTagNameEngine);
const browser = await firefox.launch();
const page = await browser.newPage();
await page.setContent(`<div><button>Click me</button></div>`);
// Use the selector prefixed with its name.
const button = await page.$('tag=button');
// Combine it with other selector engines.
await page.click('tag=div >> text="Click me"');
// Can use it in any methods supporting selectors.
const buttonCount = await page.$$eval('tag=button', buttons => buttons.length);
await browser.close();
})();
```
### param: Selectors.register.name
- `name` <[string]>
Name that is used in selectors as a prefix, e.g. `{name: 'foo'}` enables `foo=myselectorbody` selectors. May only
contain `[a-zA-Z0-9_]` characters.
### param: Selectors.register.script
- `script` <[function]|[string]|[Object]>
- `path` <[path]> Path to the JavaScript file. If `path` is a relative path, then it is resolved relative to the current working directory. Optional.
- `content` <[string]> Raw script content. Optional.
Script that evaluates to a selector engine instance.
### option: Selectors.register.contentScript
- `contentScript` <[boolean]>
Whether to run this selector engine in isolated JavaScript environment. This environment has access to the same DOM, but
not any JavaScript objects from the frame's scripts. Defaults to `false`. Note that running as a content script is not
guaranteed when this engine is used together with other registered engines.