问生产环境主机可以SSH登陆吗？

function Rep() {

    var str = 'Hello World';

    str = setCharAt(str,4,'a');

    alert(str);

}

function setCharAt(str,index,chr) {

    if(index > str.length-1) return str;

    return str.substr(0,index) + chr + str.substr(index+1);

}

<button onclick="Rep();">click</button>

String.prototype.replaceAt=function(index, replacement) {

    return this.substr(0, index) + replacement+ this.substr(index + replacement.length);

}

var hello="Hello World";

alert(hello.replaceAt(2, "!!")); //should display He!!o World