It's a core JS method, and therefore not documented in the Acrobat JS API.
The core JS API can be found here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference
It's a core JS method, and therefore not documented in the Acrobat JS API.
The core JS API can be found here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference