Javascript正则表达式

        //中括号表示指定范围
        var str = "qa123_";
        var reg = /^[a-z0-9A-Z_]{5,8}$/;
        //\w代表数字母下划线
        var regg = /^\w{5,8}$/;
        //\d代表数字0-9
        var regg = /^\d{5,8}$/;
        //\s空格或换行
        //?匹配0位或一位
        //.匹配所有
        //\转义

        //一位到多位
        var reggg = /^[0-9]{1,}$/;
        var regggg = /^[0-9]+$/;

        //test方法返回布尔值，exec返回匹配的内容
        var result = regg.exec(str);
        console.log(result);

    //匹配邮箱格式
    var input = "12w_d56@163.com"

    var reg = /^\w{5,12}@163\.com$/;

    if (reg.test(input)) {
        console.log("pass")
    } else {
        console.log("fail")
    }





    //去掉字符串中的字母
    var input = "123abc456def"

    //最后＋g全局匹配
    var word = /[a-zA - Z]/g;

    var result = input.replace(word, "")

    console.log(result)






    //截取字符串
    var input = "2021-12-01"

    //()用来分组
    var reg = /^(\d{4})-(\d{2})-(\d{2})$/;

    console.log(reg.exec(input))

    result = reg.exec(input)

    console.log(result[1]); //2021
    console.log(result[2]); //12