JavaScript Realm_basics Guide
ShadowRealm provides isolated JavaScript execution contexts with their own global scope for secure code evaluation. The guide walks through ShadowRealm Basics. `const realm = new ShadowRealm()`. Evaluate: `await realm.evaluate("1 + 2")`. Import: `await realm.importValue("./module.js", "export")`. Each realm has its own global scope and built-ins. Primitive values cross the boundary by copying. Objects cannot leak between realms. Use for: plugin systems, third-party code isolation. The guide is organized into 1 sections that build on each other, each pairing a prose explanation with runnable code. Related guides: Arrays, Strings, Numbers, Math, Date. This is one of 145 JavaScript guides on JS Reference — see the full list on the guides page. Practice what you learn in the JavaScript playground, and look up any unfamiliar term in the JavaScript glossary.