how to detect a function was called with javascript
Static variables
Here's how to create static (like in C) variables using self calling functions to store your static variables in a closure.
var myFun = (function() {
var called = false;
return function() {
if (!called) {
console.log("I've been called");
called = true;
}
}
})()
Abstract the idea
Here's a function that returns a function that only gets called once, this way we don't have to worry about adding boiler plate code to every function.
function makeSingleCallFun(fun) {
var called = false;
return function() {
if (!called) {
called = true;
return fun.apply(this, arguments);
}
}
}
var myFun = makeSingleCallFun(function() {
console.log("I've been called");
});
myFun(); // logs I've been called
myFun(); // Does nothing
Use decorator pattern.
// your function definition
function yourFunction() {}
// decorator
function callItOnce(fn) {
var called = false;
return function() {
if (!called) {
called = true;
return fn();
}
return;
}
}
yourFunction(); // it runs
yourFunction(); // it runs
yourFunction = callItOnce(yourFunction);
yourFunction(); // it runs
yourFunction(); // null
This solution provides a side-effect free way for achieving your goal. You don't have to modify your original function. It works nice even with library functions. You may assign a new name to the decorated function to preserve the original function.
var myLibraryFunction = callItOnce(libraryFunction);
myLibraryFunction(); // it runs
myLibraryFunction(); // null
libraryFunction(); // it runs