Supporting Internet Explorer
Enabling Internet Explorer Support
Internet Explorer does not natively support Symbols, Promises, or the Fetch API. Vega uses Symbols to add unique identifiers to data objects, uses Promises for asynchronous tasks such as data and image loading, and uses Fetch to load external files.
For Vega 4.3 and earlier to work with Internet Explorer, deployments should include polyfills that add Symbol, Promise, and Fetch support. For example, one can use the es6-promise and the github/fetch libraries. Web pages should first import any polyfill scripts, then import Vega:
<head> <script src="https://vega.github.io/vega/assets/promise.min.js"></script> <script src="https://vega.github.io/vega/assets/symbol.min.js"></script> <script src="https://vega.github.io/vega/assets/fetch.min.js"></script> <script src="https://vega.github.io/vega/vega.min.js"></script> </head>
Note that polyfills are necessary only for Internet Explorer support. Recent versions of other browsers – including Edge (Internet Explorer’s successor), Chrome, Safari, Firefox and Opera – all have native Symbol, Promise, and Fetch support.
Input event handling issues on Internet Explorer may arise when using stroked marks (such as
line marks) with a Canvas renderer. Some versions of Internet Explorer do not support the Canvas Context2D method
isPointInStroke. Vega depends on this method to determine when the mouse cursor is within a stroke. Without it, Vega can only tell when a point lies within a filled (rather than stroked) region, causing interactions such as mouse hover over line marks to fail. Possible solutions include using SVG rather than Canvas (Vega then uses browser element event listeners to determine hover), or encouraging users to upgrade to a more modern standards-compliant browser.