Recursively Iterate a nested structure and render strings as mustache templates

demo.js

const input = {
  email: {
    subject: 'Happy birthday {{name}} 🎂',
    body: 'Hi {{name}}, you are turning {{age}} today!'
  }
};
const ctx = { name: 'Søren', age: 30 };
const tmpl = renderMustache(input, ctx); 
// tmpl: {"email": {"subject": "Happy birthday Søren 🎂", "body": "Hi Søren, you are turning 30 today!"}}

render-mustache.js

import { isObject, isArray, isString } from 'lodash';

function renderMustache(input, ctx) {
  if (isString(input)) {
    return mustache.render(input, ctx);
  }

  if (isArray(input)) {
    return input.map(itemValue => renderMustache(itemValue, ctx));
  }

  if (isObject(input)) {
    return Object.keys(input).reduce((acc, key) => {
      const value = input[key];

      return { ...acc, [key]: renderMustache(value, ctx) };
    }, {});
  }

  return input;
}