handlebars.js/lib/handlebars/helpers/with.js

import {isEmpty, isFunction} from '../utils';
import Exception from '../exception';

export default function(instance) {
  instance.registerHelper('with', function(context, options) {
    if (arguments.length != 2) { throw new Exception('#with requires exactly one argument');}
    if (isFunction(context)) { context = context.call(this); }

    let fn = options.fn;

    if (!isEmpty(context)) {
      let data = options.data;

      return fn(context, {
        data: data,
        blockParams: [context]
      });
    } else {
      return options.inverse(this);
    }
  });
}