Take a look at Codemirror (https://codemirror.net/ https://codemirror.net/). It has support for autocompletion, although I haven't tested this myself. You can

Take a look at Codemirror (https://codemirror.net/ https://codemirror.net/). It has support for autocompletion, although I haven't tested this myself. You can also define syntax highlighting for your grammar.