JavaScript - run once without booleans

Question

Is there a way to run a piece of JavaScript code only ONCE, without using boolean flag variables to remember whether it has already been ran or not?

Spe

Answer 1

What about an immediately invoked anonymous function?

(function () {

    // code in here to run once

})();

the code will execute immediately and leave no trace in the global namespace.

If this code is going to need to be called from elsewhere, then a closure can be used to ensure that the contents of a function are run only once. Personally, I prefer this to a function that rewrites itself as I feel doing so can cause confusion, but to each their own :) This particular implementation takes advantage of the fact that 0 is a falsy value.

var once = (function() {
  var hasRun = 0;  
  return function () {
    if (!hasRun) {
      hasRun++;   

      // body to run only once

      // log to the console for a test       
      console.log("only ran once");
    }              
  }
})();

// test that the body of the function executes only once
for (var i = 0; i < 5; i++) 
  once();