javascript look help

[dice93]

Hey guys, i'm fairly new to programming in Javascript.
I've been trying to write a basic user name and password program.
I was wondering if I could get some help with how I would put it in a loop so if the information in incorrect, it will prompt up "x" amount of times until the information is correct. Thanks, here's what I have so far.

var user_name = prompt ("Please enter your username: ");
var password = prompt ("Please enter your password: ");

if( (user_name=="John123") && (password=="helloworld") ){
alert("Welcome, " + user_name + ".");
}
else{
alert (" Sorry, information invalid. " );
}

[kromol]

I think the best way to do it will be recursive function.
Something like this:

function checkCredentials(){
    var user_name = prompt("Username"),
        password = prompt("password"),
        status = (user_name === "John123") && (password === "helloworld");
    if (!status) {
        checkCredentials();
    } else {
        alert("Successful");
    }
}
checkCredentials();

[ReFreezed]

A while loop would be much better than a recursive function:

while (true) {

  var user_name = prompt("Please enter your username: ");
  var password = prompt("Please enter your password: ");

  if (user_name == "John123" && password == "helloworld") {
    alert("Welcome, " + user_name + ".");
    break;
  }
  else {
    alert("Sorry, information invalid.");
  }

}

This is however a very bad way of coding since it will completely lock the page until the information is correct! You should really use a form with inputs for name and password instead of using prompts.