Javascript: Variable as While Condition

Question

I would like to specify the while's condition as a variable, something like:

function doWhile(condition){
 while(condition){
 number++;
 }
 alert(number);
}
var number = 1;
doWhile(number < 10);

Answer 1

The only way to do this is using functions.

function doWhile(condition, action, undefined) {
 var current = undefined;
 // call your condition with the current value
 while(condition(current)) {
 // do something with the current value then update it
 current = action(current);
 }
 return result;
}
var number = doWhile(function condition(number) {
 // if the current value has no value yet continue
 // if the current value is less than 10
 return number === undefined || number < 10;
}, function action(number) {
 // if the number has no value set it to 0
 if (number === undefined) {
 number = 0;
 }
 // increase it
 return ++number;
});
console.log(number);

• user113716: What, you don't want to run eval() in a loop? ;o) +1
• Raynos: @patrick_dw I was tempted. But I decided to do it properly. Besides if I show him the eval solution, he'll go "thats easier/nicer I'll just use that. What do you mean eval is bad? eval is fine!"
• user113716: @Raynos: I saw that exact situation earlier this year, but with someone giving a solution using with. It took only a few minutes for OP to break his code, but was convinced that with was the solution anyway.
• Adam Halasz: Well, it works, but I don't really understand what's going on :S, return number === undefined || number < 10; Why do I need the number === undefined part from here?
• Raynos: @CIRK the first call is undefined. You can initialize result = 0 if you want. But then it defaults to 0 instead of undefined and wouldn't work nicely with strings or arrays. I can imagine this looking alien if your not used to passing first class functions around like this.