数组合并法（IE7性能优化）

var str = "I'm a thirty-five character string.",
    strs = [],
    newStr,
    appends = 5000;

while (appends--) {
    strs[strs.length] = str;
}

newStr = strs.join("");

以上代码为了让IE7或者更低版本的浏览器性能更优。其他浏览器使用以下代码：

var str = "I'm a thirty-five character string.",
    newStr = "",
    appends = 5000;

while (appends--) {
    newStr += str;
}