No library, at least in Firefox it's defined by devtools and only works in the console (provided the page doesn't have it's own $ and $$ globals). [0] http://d

No library, at least in Firefox it's defined by devtools and only works in the console (provided the page doesn't have it's own $ and $$ globals). [0] http://dxr.mozilla.org/mozilla-central/source/toolkit/devtools/server/actors/webconsole.js#1016 http://dxr.mozilla.org/mozilla-central/source/toolkit/devtoo... [1] http://dxr.mozilla.org/mozilla-central/source/toolkit/devtools/webconsole/utils.js#1407 http://dxr.mozilla.org/mozilla-central/source/toolkit/devtoo... Edit: It works in the WebKit devtools too: [0] https://mxr.mozilla.org/chromium/source/src/third_party/WebKit/Source/core/inspector/InjectedScriptSource.js#1315 https://mxr.mozilla.org/chromium/source/src/third_party/WebK...