Promise support

Adding the ability to return promises if a callback is not supplied to the renderFile function

var renderedString = await ejs.renderFile(filepath, {data:'data'}, {options:options})

[niftylettuce]

Would love to see this, in the meanwhile you can use util.promisify:

const { promisify } = require('util');
const ejs = require('ejs');

const renderFile = promisify(ejs.renderFile).bind(ejs);

(async () => {
  try {
    const str = await renderFile('test');
    console.log(str);
  } catch (err) {
    throw err;
  }
})();

Thoughts on adding this to the docs/README in the meanwhile @RyanZim?

Also I don’t see ejs.renderFile mentioned in the docs on the website at all, maybe we should add that to the docs section and also a note about Promise support.

[RyanZim]

@jdalrymple This would need to be in the next major release, as we currently support all the way back to Node 0.10. We’re considering a major release, and if we did do such a release, we’d definitely consider this.