JavaScript – run once without booleans

An alternative way that overwrites a function when executed so it will be executed only once.

function useThisFunctionOnce(){
   // overwrite this function, so it will be executed only once
   useThisFunctionOnce = Function("");
   // real code below
   alert("Hi!");
}

// displays "Hi!"
useThisFunctionOnce();
// does nothing
useThisFunctionOnce();

‘Useful’ example:

var preferences = {};
function read_preferences(){
   // read preferences once
   read_preferences = Function("");
   // load preferences from storage and save it in 'preferences'
}
function readPreference(pref_name){
    read_prefences();
    return preferences.hasOwnProperty(pref_name) ? preferences[pref_name] : '';
}
if(readPreference('like_javascript') != 'yes'){
   alert("What's wrong wth you?!");
}
alert(readPreference('is_stupid') ? "Stupid!" : ":)");

Edit: as CMS pointed out, just overwriting the old function with function(){} will create a closure in which old variables still exist. To work around that problem, function(){} is replaced by Function(""). This will create an empty function in the global scope, avoiding a closure.