JScript

JScript is Microsoft's legacy dialect of the standard that is used in Internet Explorer 11 and older.

History
First supported in Internet Explorer 3.0 in August 1996, its most recent version is JScript 9.0, included with Internet Explorer 9. Microsoft transitioned to the Chakra open source JScript and JavaScript engines for improved performance in the latter versions of Explorer to early versions of Microsoft Edge (now called Edge Legacy). In 2018, Edge switched to the from Google's Chromium browser platform.