~function(){
function myIndexOf(s){
let reg = new RegExp(s);
console.log(this)
let res = reg.exec(this);
if(res == null){
return -1
}else{
return res.index;
}
}
String.prototype.myIndexOf = myIndexOf;
}()
let str = 'nishibushiyigeren';
console.log(str.myIndexOf('bus'))