I presume it is possible to create a JavaScript function that disables it self after it is done running.
Is possible? How can this effect be achieved?
6 Answers
Wrap arbitrary runnable in following manner:
function once(subject) {
var first = true;
return function() {
if (first) {
first = false;
return subject();
} else {
return null;
}
};
}
var wrapper = once(function() {alert("No more!");});
wrapper(); // alerts
wrapper(); // noop
Runnable will only be executed on first invocation of wrapper.
You can convert a function of arbitrary arguments to an argumentless runnable.
Comments
If you want the functionality to be happen only once you can use the following function
function once(fn, context) {
var result;
return function() {
if(fn) {
result = fn.apply(context || this, arguments);
fn = null;
}
return result;
};
}
// Usage
var canOnlyFireOnce = once(function() {
console.log('Fired!');
});
canOnlyFireOnce(); // "Fired!"
canOnlyFireOnce(); // nada
Courtesy: https://davidwalsh.name/essential-javascript-functions
Comments
something like this?
function a(){ alert(1); a = null;}
invoke a() once, second time it will say
Uncaught TypeError: a is not a function
if the function is anonymous, then make it IIFE
(function(){ alert(1);})();
15 Comments
void
Never give up! :)
Basilevs
Will only work if function is stored in a field of original name.
var b = a; b(); b(); b(); will always alert.
gurvinder372
@Basilevs agree, I guess if OP wants to execute it only once he/she wouldn't want to store its reference in another variable, but good catch!
Rajesh Dixit
@gurvinder372 we can even have named function as IIFEs. They will not be accessible but will add readability to code.
gurvinder372
@Rajesh
we can even have named function as IIFEs agree. but add readability to code debatable, not totally sure about that. |
var _flag = true; // Have a flag variable.
function oneTimer(){
// Check flag is set to true or not
if(!_flag) return;
_flag = false;
// Your function definition here.
}
1 Comment
synthet1c
You are using a variable declared in the outer scope of the function, The accepted
once functional decorator is a much better solution as everything is enclosed within it so there can be no issues with the 'pure' function. Also this would not be reusable, once can be used on any function, but if you wanted to do the same thing to another function you would have to do something like _flag_2 which could get messy quickly.As commented, if you want to execute a function only once, you should try IIFE. These functions are invoked immediately and cannot be called afterwards.
Following is a sample code.
(function test() {
console.log("test");
(function innerFunc() {
console.log("Inner Function");
})();
try {
innerFunc();
} catch (ex) {
console.log(ex)
}
})();
try {
test();
} catch (ex) {
console.log(ex)
}
Comments
Pretty easy, just assign an empty function to the function:
function once() {
alert('once');
once = function () { };
}
once();
once();
Comments
javascript functionor do you really want to disablea javascriptIIFE. These functions are executed immediately and cannot be called.