65 lines
2.2 KiB
Markdown
65 lines
2.2 KiB
Markdown
<!-- Do not edit this file. It is automatically generated by API Documenter. -->
|
|
|
|
[Home](./index.md) > [puppeteer](./puppeteer.md) > [ExecutionContext](./puppeteer.executioncontext.md) > [evaluate](./puppeteer.executioncontext.evaluate.md)
|
|
|
|
## ExecutionContext.evaluate() method
|
|
|
|
<b>Signature:</b>
|
|
|
|
```typescript
|
|
evaluate<ReturnType extends any>(pageFunction: Function | string, ...args: unknown[]): Promise<ReturnType>;
|
|
```
|
|
|
|
## Parameters
|
|
|
|
| Parameter | Type | Description |
|
|
| --- | --- | --- |
|
|
| pageFunction | Function \| string | a function to be evaluated in the <code>executionContext</code> |
|
|
| args | unknown\[\] | argument to pass to the page function |
|
|
|
|
<b>Returns:</b>
|
|
|
|
Promise<ReturnType>
|
|
|
|
A promise that resolves to the return value of the given function.
|
|
|
|
## Remarks
|
|
|
|
If the function passed to the `executionContext.evaluate` returns a Promise, then `executionContext.evaluate` would wait for the promise to resolve and return its value. If the function passed to the `executionContext.evaluate` returns a non-serializable value, then `executionContext.evaluate` resolves to `undefined`<!-- -->. DevTools Protocol also supports transferring some additional values that are not serializable by `JSON`<!-- -->: `-0`<!-- -->, `NaN`<!-- -->, `Infinity`<!-- -->, `-Infinity`<!-- -->, and bigint literals.
|
|
|
|
## Example 1
|
|
|
|
|
|
```js
|
|
const executionContext = await page.mainFrame().executionContext();
|
|
const result = await executionContext.evaluate(() => Promise.resolve(8 * 7))* ;
|
|
console.log(result); // prints "56"
|
|
|
|
```
|
|
|
|
## Example 2
|
|
|
|
A string can also be passed in instead of a function.
|
|
|
|
```js
|
|
console.log(await executionContext.evaluate('1 + 2')); // prints "3"
|
|
|
|
```
|
|
|
|
## Example 3
|
|
|
|
[JSHandle](./puppeteer.jshandle.md) instances can be passed as arguments to the `executionContext.* evaluate`<!-- -->:
|
|
|
|
```js
|
|
const oneHandle = await executionContext.evaluateHandle(() => 1);
|
|
const twoHandle = await executionContext.evaluateHandle(() => 2);
|
|
const result = await executionContext.evaluate(
|
|
(a, b) => a + b, oneHandle, * twoHandle
|
|
);
|
|
await oneHandle.dispose();
|
|
await twoHandle.dispose();
|
|
console.log(result); // prints '3'.
|
|
|
|
```
|
|
|