javascript replaceall 正则表达式

var str = "dogdogdog";
var str2 = str.replace(/dog/g,"cat");
console.log(str2);

参考：https://www.jb51.net/article/23762.htm?tdsourcetag=s_pcqq_aiomsg

str = "dog dog dog12";
str = str.replace(new RegExp("[d]","gm"),"_");
console.log(str);

输出：_og _og _og12

 参考：https://www.runoob.com/jsref/jsref-obj-regexp.html