使用非 ES6 语法，没有字符串模板时，对字符串进行插值格式化

formatStr.js

function format (source, args) {
    var result = source;
    if (typeof(args) == "object") {
        if (args.length == undefined) {
            for (var key in args) {
                if (args[key] != undefined) {
                    var reg = new RegExp("({" + key + "})", "g");
                    result = result.replace(reg, args[key]);
                }
            }
        } else {
            for (var i = 0; i < args.length; i++) {
                if (args[i] != undefined) {
                    var reg = new RegExp("({[" + i + "]})", "g");
                    result = result.replace(reg, args[i]);
                }
            }
        }
    }
    return result;
}