+1 Zippo，但函数体需要如下所示，否则它会在每次迭代时附加当前字符串：

String.prototype.format = function() {
    var formatted = this;
    for (var arg in arguments) {
        formatted = formatted.replace("{" + arg + "}", arguments[arg]);
    }
    return formatted;
};

非常优雅：

String.prototype.format = function (){
    var args = arguments;
    return this.replace(/\{\{|\}\}|\{(\d+)\}/g, function (curlyBrack, index) {
        return ((curlyBrack == "{{") ? "{" : ((curlyBrack == "}}") ? "}" : args[index]));
    });
};

// Usage:
"{0}{1}".format("{1}", "{0}")

信贷转到（断开链接）https://gist.github.com/0i0/1519811

旧答案的修改代码https://stackoverflow.com/a/18234317/19531844效率更高（没有较慢的RegExp）且更短

String.prototype.formatUnicorn = function () {
    let str = this.toString();
    if(!arguments.length) {
        return;
    };
    const [args] = arguments;
    for (const key of Object.keys(args)) {
        str = str.replaceAll(`{${key}}`, args[key]);
    };
    return str;
};

用法：

"{test} {test_2} {test}".formatUnicorn({"test": "hello", "test_2": "world"}); // yields hello world hello

新旧基准：https://jsben.ch/BRovx

/**
 * Format string by replacing placeholders with value from element with
 * corresponsing index in `replacementArray`.
 * Replaces are made simultaneously, so that replacement values like
 * '{1}' will not mess up the function.
 *
 * Example 1:
 * ('{2} {1} {0}', ['three', 'two' ,'one']) -> 'one two three'
 *
 * Example 2:
 * ('{0}{1}', ['{1}', '{0}']) -> '{1}{0}'
 */
function stringFormat(formatString, replacementArray) {
    return formatString.replace(
        /\{(\d+)\}/g, // Matches placeholders, e.g. '{1}'
        function formatStringReplacer(match, placeholderIndex) {
            // Convert String to Number
            placeholderIndex = Number(placeholderIndex);

            // Make sure that index is within replacement array bounds
            if (placeholderIndex < 0 ||
                placeholderIndex > replacementArray.length - 1
            ) {
                return placeholderIndex;
            }

            // Replace placeholder with value from replacement array
            return replacementArray[placeholderIndex];
        }
    );
}

我使用一个名为String.format for JavaScript的小型库，它支持大多数格式字符串功能（包括数字和日期格式），并使用.NET语法。脚本本身小于4kB，因此不会产生太多开销。

一个稍有不同的版本，我更喜欢的版本（这个版本使用｛xxx｝标记，而不是｛0｝编号的参数，这更易于自我记录，更适合本地化）：

String.prototype.format = function(tokens) {
  var formatted = this;
  for (var token in tokens)
    if (tokens.hasOwnProperty(token))
      formatted = formatted.replace(RegExp("{" + token + "}", "g"), tokens[token]);
  return formatted;
};

一种变化是：

  var formatted = l(this);

它首先调用l（）本地化函数。