一个优雅的 String.format 简单实现

// 这份代码片段基于Public Domain发布
String.format = function(tpl) {
    var index = 1, items = arguments;
    return (tpl || '').replace(/{(\w*)}/g, function(match, p1) {
        return items[index++] || p1 || match;
    });
};
String.prototype.format = function() {
    var index = 0, items = arguments;
    return this.replace(/{(\w*)}/g, function(match, p1) {
        return items[index++] || p1 || match;
    });
};

> 'test{}test{}'.format()
< "test{}test{}"
> 'test{}test{2}'.format('1')
< "test1test2"
> 'test{}test{2}'.format('1', '3')
< "test1test3"