哪个正则表达式更快？ [关闭]

Question

如果我想匹配A 或a，以下哪个正则表达式会更快找到它？

/[Aa]/

或

/A/i

如何 many steps it 是怎么做的？

Answer 1

尝试像这样检查它：

function time_my_script(script) {
    var start = window.performance.now();
    script();
    return window.performance.now() - start;
}

time_a = time_my_script(function() {
    var text = 'This is a test string, make it a long one to actually test well';
    var patt = new RegExp(/[Aa]/);
    var res = patt.test(text);
});

time_b = time_my_script(function() {
    var text = 'This is a test string, make it a long one to actually test well';
    var patt = new RegExp(/A/i);
    var res = patt.test(text);
});

console.log('Time A ' + time_a);
console.log('Time B ' + time_b);

JSFiddle：https://jsbin.com/gasayarivu/edit?js,console

PS：
使用异步脚本，这可能会有点困难。