src/locale/format.js

/**
 *  String format template
 *  - Inspired:
 *    https://github.com/Matt-Esch/string-template/index.js
 */
const RE_NARGS = /(%|)\{([0-9a-zA-Z_]+)\}/g;
export default function(Vue) {
    // const { hasOwn } = Vue.util;
    function hasOwn (obj, key) {
        return Object.prototype.hasOwnProperty.call(obj, key);
    }
    /**
     * template
     *
     * @param {String} string
     * @param {Array} ...args
     * @return {String}
     */
    function template(string, ...args) {
        if (args.length === 1 && typeof args[0] === 'object') {
            args = args[0];
        }
        if (!args || !args.hasOwnProperty) {
            args = {};
        }
        return string.replace(RE_NARGS, (match, prefix, i, index) => {
            let result;
            if (string[index - 1] === '{' &&
                string[index + match.length] === '}') {
                return i;
            } else {
                result = hasOwn(args, i) ? args[i] : null;
                if (result === null || result === undefined) {
                    return '';
                }
                return result;
            }
        });
    }
    return template;
}