Ghost/ghost/tpl/lib/tpl.js

const template = require('lodash.template');
const interpolate = /(?<!{){([^{]+?)}/g;

/**
 * Template function
 * Takes strings like 'Your site is now available on {url}' and interpolates them with passed in data
 * Will ignore double or triple braces like {{get}} or {{{helpername}}}
 * Can handle escaped braces e.g. \\{\\{{helpername}\\}\\}
 * But there's a simple bare minimum escaping needed to make {{{helpername}}} work e.g. {\\{{helpername}}}
 *
 *
 * @param {String} string - string with optional {data properties}
 * @param {Object} [data] - optional data to interpolate
 * @returns {string} the interpolated string
 */
module.exports = (string, data) => {
    if (!data) {
        return string;
    }

    // We replace any escaped left braces with the unicode character so we can swap it back later
    let processedString = string.replace(/\\{/g, '\\U+007B');
    // Let lodash do its thing
    processedString = template(processedString, {interpolate})(data);
    // Replace our swapped out left braces and any escaped right braces
    return processedString.replace(/\\U\+007B/g, '{').replace(/\\}/g, '}');
};