ECMAScript 5's strict mode is a way to opt in to a restricted variant of JavaScript. Strict mode isn't just a subset: it intentionally has different semantics from normal code. Browsers not supporting strict mode will run strict mode code with different behavior from browsers that do, so don't rely on strict mode without feature-testing for support for the relevant aspects of strict mode. Strict mode code and non-strict mode code can coexist, so scripts can opt into strict mode incrementally.
A strict-mode-only warning that a ReferenceError occurred. JavaScript execution won't be halted.
The mode read-only property of the Request interface contains the mode of the request (e.g., cors, no-cors, cors-with-forced-preflight, same-origin, or navigate.) This is used to determine if cross-origin requests lead to valid responses, and which properties of the response are readable:
display-mode is a CSS media feature that selectively applies CSS based on the display mode of the application. This feature corresponds the Web app manifest's display member. Both apply to the top-level browsing context and any child browsing contexts. This query applies regardless of whether a web app manifest is present. Use this query to provide a consistant user experience between launching a site from an URL and lunching it from a desktop icon.
An IDBTransactionMode object defining the mode for isolating access to data in the current object stores:
The mode property of the SourceBuffer interface controls whether media segments can be appended to the SourceBuffer in any order, or in a strict sequence.