字符串的正则表达式

str.search()：返回第一个匹配的子串的位置，不支持全局
str.replace(reg,function(){})：匹配并替换
str.match(reg)：将所有的匹配结果放到一个数组中
str.split(reg)：按照正则匹配到的内容切割

举个栗子🌰

var reg = /\d{2}/g;
var str = "ab3f12fa34";
console.log(str.search(reg));   // 4

var reg = /\d{2}/g;
var str = "ab3f12fa34";
console.log(str.replace(reg,"**"));   // ab3f**fa**

var reg = /\d{2}/g;
var str = "ab3f12fa34";
console.log(str.match(reg));   // ["12", "34"]

var reg = /\d{2}/g;
var str = "ab3f12fa34";
console.log(str.split(reg));   // ["ab3f", "fa", ""]

var pattern = /box/i;
var str = 'this is a box,that is a box';
alert(str.match(pattern));          //不是全局匹配，将返回一个box

var pattern = /box/ig;
var str = "this is a box,that is a box";
alert(str.match(pattern));          //开启了全局，这里将返回所有满足条件的字符串，所以是box，box

var pattern = /Box/ig;          //开启全局替换
var str = "this is a box,that is a Box";
alert(str.replace(pattern,"dog"));          //找到字符串中和模式相同的字符串，用新的字符串dog替换

var pattern = /Box/i;
var str = "this is a box ,that is a box";
alert(str.replace(pattern,"dog"));          // 局部匹配，只将第一个字符串匹配成dog(this is a dog,that is a box)

var pattern = /Box/i;
var str = "this is a box ,that is a box";
alert(str.search(pattern));             //返回pattern第一次出现的位置，只要有就返回一个数，没有就返回-1，所以search没有全局与局部之分

var pattern = /hello/i;
var str = "this is a box ,that is a box";
alert(str.search(pattern));                 //str中没有与模式相匹配的字符串，所以这个返回-1

var pattern = / /ig;
var str = "this is a box ,that is a box";
alert(str.split(pattern));              //返回一个数组，包含了按照pattern划分之后的字符串数组