Javascript replace the placeholder

String.prototype.format=function(){
    if(arguments.length===0){
        return String(this);
    }
    let reg=/(\{\d\})/;
    let r=this;
    while(reg.test(r)){
        let index=RegExp.$1.slice(1,-1);
        r = r.replace(new RegExp("\\{"+index+"\\}","g"),(index >= arguments.length)?"":arguments[index]);
    }
    return r;
};

Javascript string replace the placeholder

"" Hello, I'm {0}, {2} years old this year, gender {1} end of the test ".format ( 'Devil', 'M', '18 ' ) 
 " Hello, I am the devil, this year 18 years old, male gender, the end of the test