示例：

备选字符集

var str ="上海，上天，上哪里去";
var reg =/上[海天]/g
console.log(str.replace(reg,"*"));  // *，*，上哪里去
var str = "上海，上天，上哪里"
var reg = /[上天哪]/g
console.log(str.replace(reg,"*"));  // *海，**，**里
var res = "ajkdgkbcj128973489"
var reg = /[0-9]/g
console.log(res.replace(reg,"*"));  // ajkdgkbcj*********
var str = "hello"
var reg = /[el]o/g
console.log(str.replace(reg,"*"));  // hel*

转义字符

var str = "https://www.baidu.com"
var str2 = "http://www.baidu.com"
var reg = /(http|https):\/\/[w]{3}\.baidu\.com/
console.log(reg.test(str));
console.log(reg.test(str2));

指定匹配的位置

// 电话
var num = "13897932473123"
var reg = /^1[3-9]\d{9}$/
console.log(reg.test(num));

<input type="text" id="input">
<script>
  /* 去除开头结尾的空格 */
  var res = []
  var reg = /^\s+|\s+$/g;
  var input = document.getElementById("input")
  input.onkeydown = function(event){
    if(event.keyCode == 13){
      var str = this.value
      res.push(str.replace(reg,""))
      console.log(res);
    }
  }
</script>

非

var str = "abc123";
var reg = /[^abc]/g;
console.log(str.replace(reg,"*"));  //abc***
var test = "?@hello123-";
var re = /[^\d]/g;
console.log(test.replace(re,"*"));  //*******123*
var str = "hello210874"
var reg = /[^a-z]/g
console.log(str.replace(reg,""));  // hello
var str = "<p>我是p标签</p>。<div>我是div</div>"
var reg = /<[^<>]+>/g
console.log(str.replace(reg,""));  // 我是p标签。我是div
var str = "https://movie.douban.com/subject/129205/"
var reg = /[^\d+]/g
console.log(str.replace(reg,"")); // 129205

表单验证

手机号验证
<input type="text" id="app">
    <script>
         var reg = /^(086)?1[3-9]\d{9}$/ ;
         $("#app").keydown(function(event){
             if(event.keyCode == 13){
                 var value = $(this).val();
                 console.log(reg.test(value))
             }
         })
    </script>

身份证号验证
 <script>
        /*
        42......x
        42900619881024307x 
        42\d{15}(\d|x)
        42\d{15}[\dx]
         */
        var str = "42900619881024307x";
        var reg = /^42\d{15}[\dx]$/;
        console.log(reg.test(str))
    </script>

邮箱验证
  39775347@qq.com
  cheng_chao@sina.com
   <script>      
        var reg = /^\w+@[a-z]+\.com$/
        $("input").keydown(function(event){
            if(event.keyCode==13){
                var value = $(this).val();
                console.log(value)
                console.log(reg.test(value))
            }
        })
    </script>

指定匹配位置

var str = "fdjfj121"
        var reg = /^[0-9]+/;
        console.log(reg.test(str))   //false
        console.log(/\d+$/.test(str))   //true
        var str = "   hello    ";
        var reg = /(^\s+)|(\s+$)/g
        console.log(str.trim())          //hello
        console.log(str.replace(reg,""))    //hello

获取数字变成数组

<script>
        var str = "<span>2395人参观</span>-<span>46人评价</span>"
        /*
        var arr = [2395,46] 
         */
        var reg = /[^\d-]/g;
        var res = str.replace(reg,"");
        console.log(res.split("-"))
    </script>

处理文本内容

<p class="">
        导演: 陈凯歌 Kaige Chen&nbsp;&nbsp;&nbsp;主演: 张国荣 Leslie Cheung / 张丰毅 Fengyi Zha...<br>
        1993&nbsp;/&nbsp;中国大陆&nbsp;/&nbsp;剧情 爱情 同性
    </p>
    <script>
        /* [1993,中国大陆,剧情,爱情,同性] */
        /* 1993&nbsp;/&nbsp;中国大陆&nbsp;/&nbsp;剧情 爱情 同性 */
        var str =  $("p").html().trim().split("<br>")[1].trim();
        var reg = /&nbsp;/g
        var res = str.replace(reg,"")
        var arr = res.split("/")
        var last = arr[arr.length-1].split(" ");
        console.log(last)
        var sum = [arr[0],arr[1],...last];
        // for( var i=0;i<arr.length;i++){
        //     if(i<arr.length-1){
        //         sum.push(arr[i])
        //     }
        // }
        // sum.push(...last)
        console.log(sum)
  </script>
<script>
        var url = "https://movie.douban.com/subject/129205/";
        /* [[1,2],[9,2],[0,5]] */
        var reg = /[^\d]/g;
        var str = url.replace(reg,"");
        var sum = [];
        for(var i=0;i<str.length;i+=2){
            var item = str.substr(i,2).split("");
            sum.push(item);
        }
        console.log(sum)
    </script>