addInitScript
Overview
Run a function in new documents of the current tab or window before page scripts execute. Use this to prepare browser-side values before the application reads them. The function also runs in newly attached or navigated child frames within that top-level browsing context.
The script is registered for the tab or window that is current when addInitScript is called. It does not automatically apply to other tabs or windows, including those opened later. To use it there, switch to the target tab or window and register it separately before navigation.
Usage
browser.addInitScript(script, ...args)
Parameters
| Parameter | Type | Default | Description |
|---|---|---|---|
script | Function | Required | A function executed in the browser, without access to Node.js variables. |
args | unknown[] | [] | Arguments serialized as JSON and passed to the function. |
Result
Promise<InitScript>: an object with asynchronous remove() and on("data", listener). To send data to Node.js, call the emit callback appended to the script arguments.
Limitations
Requires a WebDriver BiDi session (webSocketUrl: true). Call the command before navigation. remove() prevents future injection; it does not undo changes already made in the current document. Remove the script in the same test, even if an assertion fails. In this version the implementation accepts a function, not a string.
Example
Set baseUrl to your local HTTP test site, where / returns an HTML page. Run the example in a regular Testplane test file.
const assert = require("node:assert/strict");
it("addInitScript: set a value before page scripts", async ({ browser }) => {
const script = await browser.addInitScript(value => {
window.exampleSeed = value;
}, 42);
try {
await browser.url("/");
assert.equal(await browser.execute(() => window.exampleSeed), 42);
} finally {
await script.remove();
}
await browser.url("/");
assert.equal(await browser.execute(() => typeof window.exampleSeed), "undefined");
});