Document express usage

Allow ‘root’ opt passed in data

var _OPTS = ['delimiter', 'scope', 'context', 'debug', 'compileDebug',
  'client', '_with', 'rmWhitespace', 'strict', 'filename',
  'root'
];

[mde]

Thank you so much for unraveling this! We need to add this to docs, so other people know how to do bespoke config for EJS using Express.

[nwoltman]

Actually, I can pass in options to EJS by using a custom render function with Express:

const app = express();
const ejsOptions = {
  cache: app.get('view cache'),
  root: '/path/to/views',
};

app.engine('ejs', (path, data, cb) => {
  ejs.renderFile(path, data, ejsOptions, cb);
});

This solves my problem and is probably the best way to configure EJS with Express rather than setting the completely undocumented 'view options' setting on the app.