Develop Reference

How to resolve a promise with a parameter in setTimeout [duplicate]

I have some JavaScript code that looks like:
function statechangedPostQuestion()
{
//alert("statechangedPostQuestion");
if (xmlhttp.readyState==4)
{
var topicId = xmlhttp.responseText;
setTimeout("postinsql(topicId)",4000);
}
}
function postinsql(topicId)
{
//alert(topicId);
}
I get an error that topicId is not defined
Everything was working before I used the setTimeout() function.
I want my postinsql(topicId) function to be called after some time.
What should I do?

setTimeout(function() {
postinsql(topicId);
}, 4000)
You need to feed an anonymous function as a parameter instead of a string, the latter method shouldn't even work per the ECMAScript specification but browsers are just lenient. This is the proper solution, don't ever rely on passing a string as a 'function' when using setTimeout() or setInterval(), it's slower because it has to be evaluated and it just isn't right.
UPDATE:
As Hobblin said in his comments to the question, now you can pass arguments to the function inside setTimeout using Function.prototype.bind().
Example:
setTimeout(postinsql.bind(null, topicId), 4000);

In modern browsers (ie IE11 and beyond), the "setTimeout" receives a third parameter that is sent as parameter to the internal function at the end of the timer.
Example:
var hello = "Hello World";
setTimeout(alert, 1000, hello);
More details:
https://developer.mozilla.org/en-US/docs/Web/API/WindowTimers.setTimeout
http://arguments.callee.info/2008/11/10/passing-arguments-to-settimeout-and-setinterval/

After doing some research and testing, the only correct implementation is:
setTimeout(yourFunctionReference, 4000, param1, param2, paramN);
setTimeout will pass all extra parameters to your function so they can be processed there.
The anonymous function can work for very basic stuff, but within instance of a object where you have to use "this", there is no way to make it work.
Any anonymous function will change "this" to point to window, so you will lose your object reference.

This is a very old question with an already "correct" answer but I thought I'd mention another approach that nobody has mentioned here. This is copied and pasted from the excellent underscore library:
_.delay = function(func, wait) {
var args = slice.call(arguments, 2);
return setTimeout(function(){ return func.apply(null, args); }, wait);
};
You can pass as many arguments as you'd like to the function called by setTimeout and as an added bonus (well, usually a bonus) the value of the arguments passed to your function are frozen when you call setTimeout, so if they change value at some point between when setTimeout() is called and when it times out, well... that's not so hideously frustrating anymore :)
Here's a fiddle where you can see what I mean.

I recently came across the unique situation of needing to use a setTimeout in a loop. Understanding this can help you understand how to pass parameters to setTimeout.
Method 1
Use forEach and Object.keys, as per Sukima's suggestion:
var testObject = {
prop1: 'test1',
prop2: 'test2',
prop3: 'test3'
};
Object.keys(testObject).forEach(function(propertyName, i) {
setTimeout(function() {
console.log(testObject[propertyName]);
}, i * 1000);
});
I recommend this method.
Method 2
Use bind:
var i = 0;
for (var propertyName in testObject) {
setTimeout(function(propertyName) {
console.log(testObject[propertyName]);
}.bind(this, propertyName), i++ * 1000);
}
JSFiddle: http://jsfiddle.net/MsBkW/
Method 3
Or if you can't use forEach or bind, use an IIFE:
var i = 0;
for (var propertyName in testObject) {
setTimeout((function(propertyName) {
return function() {
console.log(testObject[propertyName]);
};
})(propertyName), i++ * 1000);
}
Method 4
But if you don't care about IE < 10, then you could use Fabio's suggestion:
var i = 0;
for (var propertyName in testObject) {
setTimeout(function(propertyName) {
console.log(testObject[propertyName]);
}, i++ * 1000, propertyName);
}
Method 5 (ES6)
Use a block scoped variable:
let i = 0;
for (let propertyName in testObject) {
setTimeout(() => console.log(testObject[propertyName]), i++ * 1000);
}
Though I would still recommend using Object.keys with forEach in ES6.

Hobblin already commented this on the question, but it should be an answer really!
Using Function.prototype.bind() is the cleanest and most flexible way to do this (with the added bonus of being able to set the this context):
setTimeout(postinsql.bind(null, topicId), 4000);
For more information see these MDN links:
https://developer.mozilla.org/en/docs/DOM/window.setTimeout#highlighter_547041
https://developer.mozilla.org/en/docs/JavaScript/Reference/Global_Objects/Function/bind#With_setTimeout

You can pass the parameter to the setTimeout callback function as:
setTimeout(function, milliseconds, param1, param2, ...)
eg.
function myFunction() {
setTimeout(alertMsg, 3000, "Hello");
}
function alertMsg(message) {
alert(message)
}

Some answers are correct but convoluted.
I am answering this again, 4 years later, because I still run into overly complex code to solve exactly this question. There IS an elegant solution.
First of all, do not pass in a string as the first parameter when calling setTimeout because it effectively invokes a call to the slow "eval" function.
So how do we pass in a parameter to a timeout function? By using closure:
settopic=function(topicid){
setTimeout(function(){
//thanks to closure, topicid is visible here
postinsql(topicid);
},4000);
}
...
if (xhr.readyState==4){
settopic(xhr.responseText);
}
Some have suggested using anonymous function when calling the timeout function:
if (xhr.readyState==4){
setTimeout(function(){
settopic(xhr.responseText);
},4000);
}
The syntax works out. But by the time settopic is called, i.e. 4 seconds later, the XHR object may not be the same. Therefore it's important to pre-bind the variables.

I know its been 10 yrs since this question was asked, but still, if you have scrolled till here, i assume you're still facing some issue. The solution by Meder Omuraliev is the simplest one and may help most of us but for those who don't want to have any binding, here it is:
Use Param for setTimeout
setTimeout(function(p){
//p == param1
},3000,param1);
Use Immediately Invoked Function Expression(IIFE)
let param1 = 'demon';
setTimeout(function(p){
// p == 'demon'
},2000,(function(){
return param1;
})()
);
Solution to the question
function statechangedPostQuestion()
{
//alert("statechangedPostQuestion");
if (xmlhttp.readyState==4)
{
setTimeout(postinsql,4000,(function(){
return xmlhttp.responseText;
})());
}
}
function postinsql(topicId)
{
//alert(topicId);
}

Replace
setTimeout("postinsql(topicId)", 4000);
with
setTimeout("postinsql(" + topicId + ")", 4000);
or better still, replace the string expression with an anonymous function
setTimeout(function () { postinsql(topicId); }, 4000);
EDIT:
Brownstone's comment is incorrect, this will work as intended, as demonstrated by running this in the Firebug console
(function() {
function postinsql(id) {
console.log(id);
}
var topicId = 3
window.setTimeout("postinsql(" + topicId + ")",4000); // outputs 3 after 4 seconds
})();
Note that I'm in agreeance with others that you should avoid passing a string to setTimeout as this will call eval() on the string and instead pass a function.

My answer:
setTimeout((function(topicId) {
return function() {
postinsql(topicId);
};
})(topicId), 4000);
Explanation:
The anonymous function created returns another anonymous function. This function has access to the originally passed topicId, so it will not make an error. The first anonymous function is immediately called, passing in topicId, so the registered function with a delay has access to topicId at the time of calling, through closures.
OR
This basically converts to:
setTimeout(function() {
postinsql(topicId); // topicId inside higher scope (passed to returning function)
}, 4000);
EDIT: I saw the same answer, so look at his. But I didn't steal his answer! I just forgot to look. Read the explanation and see if it helps to understand the code.

The easiest cross browser solution for supporting parameters in setTimeout:
setTimeout(function() {
postinsql(topicId);
}, 4000)
If you don't mind not supporting IE 9 and lower:
setTimeout(postinsql, 4000, topicId);
https://developer.mozilla.org/en-US/docs/Web/API/WindowTimers/setTimeout

I know it's old but I wanted to add my (preferred) flavour to this.
I think a pretty readable way to achieve this is to pass the topicId to a function, which in turn uses the argument to reference the topic ID internally. This value won't change even if topicId in the outside will be changed shortly after.
var topicId = xmlhttp.responseText;
var fDelayed = function(tid) {
return function() {
postinsql(tid);
};
}
setTimeout(fDelayed(topicId),4000);
or short:
var topicId = xmlhttp.responseText;
setTimeout(function(tid) {
return function() { postinsql(tid); };
}(topicId), 4000);

The answer by David Meister seems to take care of parameters that may change immediately after the call to setTimeout() but before the anonymous function is called. But it's too cumbersome and not very obvious. I discovered an elegant way of doing pretty much the same thing using IIFE (immediately inviked function expression).
In the example below, the currentList variable is passed to the IIFE, which saves it in its closure, until the delayed function is invoked. Even if the variable currentList changes immediately after the code shown, the setInterval() will do the right thing.
Without this IIFE technique, the setTimeout() function will definitely get called for each h2 element in the DOM, but all those calls will see only the text value of the last h2 element.
<script>
// Wait for the document to load.
$(document).ready(function() {
$("h2").each(function (index) {
currentList = $(this).text();
(function (param1, param2) {
setTimeout(function() {
$("span").text(param1 + ' : ' + param2 );
}, param1 * 1000);
})(index, currentList);
});
</script>

In general, if you need to pass a function as a callback with specific parameters, you can use higher order functions. This is pretty elegant with ES6:
const someFunction = (params) => () => {
//do whatever
};
setTimeout(someFunction(params), 1000);
Or if someFunction is first order:
setTimeout(() => someFunction(params), 1000);

Note that the reason topicId was "not defined" per the error message is that it existed as a local variable when the setTimeout was executed, but not when the delayed call to postinsql happened. Variable lifetime is especially important to pay attention to, especially when trying something like passing "this" as an object reference.
I heard that you can pass topicId as a third parameter to the setTimeout function. Not much detail is given but I got enough information to get it to work, and it's successful in Safari. I don't know what they mean about the "millisecond error" though. Check it out here:
http://www.howtocreate.co.uk/tutorials/javascript/timers

How i resolved this stage ?
just like that :
setTimeout((function(_deepFunction ,_deepData){
var _deepResultFunction = function _deepResultFunction(){
_deepFunction(_deepData);
};
return _deepResultFunction;
})(fromOuterFunction, fromOuterData ) , 1000 );
setTimeout wait a reference to a function, so i created it in a closure, which interprete my data and return a function with a good instance of my data !
Maybe you can improve this part :
_deepFunction(_deepData);
// change to something like :
_deepFunction.apply(contextFromParams , args);
I tested it on chrome, firefox and IE and it execute well, i don't know about performance but i needed it to be working.
a sample test :
myDelay_function = function(fn , params , ctxt , _time){
setTimeout((function(_deepFunction ,_deepData, _deepCtxt){
var _deepResultFunction = function _deepResultFunction(){
//_deepFunction(_deepData);
_deepFunction.call( _deepCtxt , _deepData);
};
return _deepResultFunction;
})(fn , params , ctxt)
, _time)
};
// the function to be used :
myFunc = function(param){ console.log(param + this.name) }
// note that we call this.name
// a context object :
myObjet = {
id : "myId" ,
name : "myName"
}
// setting a parmeter
myParamter = "I am the outer parameter : ";
//and now let's make the call :
myDelay_function(myFunc , myParamter , myObjet , 1000)
// this will produce this result on the console line :
// I am the outer parameter : myName
Maybe you can change the signature to make it more complient :
myNass_setTimeOut = function (fn , _time , params , ctxt ){
return setTimeout((function(_deepFunction ,_deepData, _deepCtxt){
var _deepResultFunction = function _deepResultFunction(){
//_deepFunction(_deepData);
_deepFunction.apply( _deepCtxt , _deepData);
};
return _deepResultFunction;
})(fn , params , ctxt)
, _time)
};
// and try again :
for(var i=0; i<10; i++){
myNass_setTimeOut(console.log ,1000 , [i] , console)
}
And finaly to answer the original question :
myNass_setTimeOut( postinsql, 4000, topicId );
Hope it can help !
ps : sorry but english it's not my mother tongue !

this works in all browsers (IE is an oddball)
setTimeout( (function(x) {
return function() {
postinsql(x);
};
})(topicId) , 4000);

if you want to pass variable as param lets try this
if requirement is function and var as parmas then try this
setTimeout((param1,param2) => {
alert(param1 + param2);
postinsql(topicId);
},2000,'msg1', 'msg2')
if requirement is only variables as a params then try this
setTimeout((param1,param2) => { alert(param1 + param2) },2000,'msg1', 'msg2')
You can try this with ES5 and ES6

setTimeout is part of the DOM defined by WHAT WG.
https://html.spec.whatwg.org/multipage/timers-and-user-prompts.html
The method you want is:—
handle = self.setTimeout( handler [, timeout [, arguments... ] ] )
Schedules a timeout to run handler after timeout milliseconds. Any
arguments are passed straight through to the handler.
setTimeout(postinsql, 4000, topicId);
Apparently, extra arguments are supported in IE10. Alternatively, you can use setTimeout(postinsql.bind(null, topicId), 4000);, however passing extra arguments is simpler, and that's preferable.
Historical factoid: In days of VBScript, in JScript, setTimeout's third parameter was the language, as a string, defaulting to "JScript" but with the option to use "VBScript". https://learn.microsoft.com/en-us/previous-versions/windows/internet-explorer/ie-developer/platform-apis/aa741500(v%3Dvs.85)

You can try default functionality of 'apply()' something like this, you can pass more number of arguments as your requirement in the array
function postinsql(topicId)
{
//alert(topicId);
}
setTimeout(
postinsql.apply(window,["mytopic"])
,500);

//Some function, with some arguments, that need to run with arguments
var a = function a(b, c, d, e){console.log(b, c, d, e);}
//Another function, where setTimeout using for function "a", this have the same arguments
var f = function f(b, c, d, e){ setTimeout(a.apply(this, arguments), 100);}
f(1,2,3,4); //run
//Another function, where setTimeout using for function "a", but some another arguments using, in different order
var g = function g(b, c, d, e){ setTimeout(function(d, c, b){a.apply(this, arguments);}, 100, d, c, b);}
g(1,2,3,4);

#Jiri Vetyska thanks for the post, but there is something wrong in your example.
I needed to pass the target which is hovered out (this) to a timed out function and I tried your approach. Tested in IE9 - does not work.
I also made some research and it appears that as pointed here the third parameter is the script language being used. No mention about additional parameters.
So, I followed #meder's answer and solved my issue with this code:
$('.targetItemClass').hover(ItemHoverIn, ItemHoverOut);
function ItemHoverIn() {
//some code here
}
function ItemHoverOut() {
var THIS = this;
setTimeout(
function () { ItemHoverOut_timeout(THIS); },
100
);
}
function ItemHoverOut_timeout(target) {
//do something with target which is hovered out
}
Hope, this is usefull for someone else.

As there is a problem with the third optonal parameter in IE and using closures prevents us from changing the variables (in a loop for example) and still achieving the desired result, I suggest the following solution.
We can try using recursion like this:
var i = 0;
var hellos = ["Hello World1!", "Hello World2!", "Hello World3!", "Hello World4!", "Hello World5!"];
if(hellos.length > 0) timeout();
function timeout() {
document.write('<p>' + hellos[i] + '<p>');
i++;
if (i < hellos.length)
setTimeout(timeout, 500);
}
We need to make sure that nothing else changes these variables and that we write a proper recursion condition to avoid infinite recursion.

// These are three very simple and concise answers:
function fun() {
console.log(this.prop1, this.prop2, this.prop3);
}
let obj = { prop1: 'one', prop2: 'two', prop3: 'three' };
let bound = fun.bind(obj);
setTimeout(bound, 3000);
// or
function funOut(par1, par2, par3) {
return function() {
console.log(par1, par2, par3);
}
};
setTimeout(funOut('one', 'two', 'three'), 5000);
// or
let funny = function(a, b, c) { console.log(a, b, c); };
setTimeout(funny, 2000, 'hello', 'worldly', 'people');

// These are three very simple and concise answers:
function fun() {
console.log(this.prop1, this.prop2, this.prop3);
}
let obj = { prop1: 'one', prop2: 'two', prop3: 'three' };
let bound = fun.bind(obj);
setTimeout(bound, 3000);
// or
function funOut(par1, par2, par3) {
return function() {
console.log(par1, par2, par3);
}
};
setTimeout(funOut('one', 'two', 'three'), 5000);
// or
let funny = function(a, b, c) { console.log(a, b, c); };
setTimeout(funny, 2000, 'hello', 'worldly', 'people');

I think you want:
setTimeout("postinsql(" + topicId + ")", 4000);

You have to remove quotes from your setTimeOut function call like this:
setTimeout(postinsql(topicId),4000);

Answering the question but by a simple addition function with 2 arguments.
var x = 3, y = 4;
setTimeout(function(arg1, arg2) {
return () => delayedSum(arg1, arg2);
}(x, y), 1000);
function delayedSum(param1, param2) {
alert(param1 + param2); // 7
}

How setTimeout works?

I have a concern with setTimeout function in javascript. when we call setTimeout function without return anything, it is okay for me. like
setTimeout(function() {
console.log("ok function called")
},2000);
here in the above example it just simply call that function after 2000ms,
And if I write this like
setTimeout(function(params) {
console.log("passed value is"+params)
},2000,55);
now it will call this function with 55 as an argument, right?
But problem is that when I call to write this like
setTimeout(function(params) {
console.log("passed value is"+params)
}(55),2000);
here function is calling with 55 as params but it is now waiting for 2000ms
And when I wrote like
setTimeout(function(params) {
console.log("passed value is "+params);
return function(){
console.log(params)
};
}(55),2000);
in this only return function is calling with 2000ms delay, the line console.log("passed value is "+params); is executing instantly
please help me get out of this problem.

One is a function. Another is a function call.
First, let's forget javascript for now. If you know any other programming language, what do you expect the two pieces of code below to do?
function a () { return 1 }
x = a;
y = a();
What do you expect x to be? 1 or a pointer to function a?
What do you expect y to be? 1 or a pointer to function a?
A function is not a function call. When you call a function it returns a value.
Now let's switch back to javascript. Whenever I get confused by a piece of code, I try to make the syntax simpler so that I can understand what's going on:
setTimeout(function() {console.log("ok function called")}, 2000);
Now, that's a compact piece of code, let's make the syntax simpler. The above code is the same as:
var a = function() {console.log("ok function called")};
setTimeout(a, 2000);
So what does that do? It will call the function a after 2 seconds.
Now let's take a look at:
setTimeout(function() {console.log("ok function called")}(), 2000);
// Note this ----------^^
That's the same as:
var b = function() {console.log("ok function called")}();
setTimeout(b, 2000);
which can further be simplified to:
var a = function() {console.log("ok function called")};
var b = a();
setTimeout(b, 2000);
So I hope you see what you're really passing to setTimeout. You're passing the return value of the function, not the function.

When you write
setTimeout(function (params) { return something; }(55), 2000);
what actually happens is something like this:
var _temp_func = function (params) { return something; };
var _temp = _temp_func(55);
setTimeout(_temp, 2000);
The anonymous function you have as a parameter to setTimeout is evaluated immediately, even before the call to setTimeout itself. In contrast to that, the actual parameter that ends up in _temp here is called with a delay. This is what happens in your last example.

setTimeout takes only function name without parenthesis.
correct syntax : setTimeout(Helloworld) - here you are setting function
incorrect syntax : setTimeout(HelloWorld()) - here you are calling function
or non IIFE function.
It's an IIFE that you are passing hence it is getting called immediately.
setTimeout(function (params) { return something; }(55), 2000);

Implementation for a function 'callAfter' that enables any function to be called after some specified duration

Edit: This is not the duplicate of how to pass params in setTimeout. Actually, I want to know how can write a function that would be called as a method on the predefined function just like the setTimeout API.
So, How can I write an implementation for a function 'callAfter' that enables any function to be called after some specified duration with certain parameters, with the following mentioned syntax:
Example: Lets say you have a function called 'sum' like so:
function sum(a, b) {
console.log('Sum is: ', a + b);
}
Now you should be able to execute:
sum.callAfter(5000, 8, 9);
which should invoke the function 'sum' after 5 seconds with parameters 8 and 9.

Got it using Function prototyping:
Function.prototype.callAfter = function(){
if(arguments.length > 1){
var args = Array.prototype.slice.call(arguments);
var time = args.splice(0,1);
var func = this;
setTimeout(function(){
func.apply(null, args);
}, time);
}
}

Calling function from array using setTimeout in Javascript

I am creating two function name call and call2 and putting this two functions in array x. In another function called timer i am trying to call this function every 2 seconds. But its giving error expected an assigment or function call instead show and expression.
And also i dont want this functions to run when i create an array.
this my code http://jsbin.com/IMiVadE/2/
function call(name)
{
console.log("Hello " + name);
}
function call2()
{
console.log("Hello world");
}
var x = [call("Nakib"), call2()];
var i = 0;
function timer(x, i)
{
x[i];
i++;
if(i<x.length)
window.setTimeout(timer(x, i), 2000);
}
timer(x, i);

You have some mistakes in your code:
call2() calls the function. Correct: call2 is the reference to the function.
x[i] accesses the value (the function reference). You need x[i]() to execute the function.
Here is your code working: http://jsbin.com/IMiVadE/6/edit
sayHello(name) is a function that generates new functions that output a specific "Hello ..." text.
function sayHello(name)
{
return function () {
console.log("Hello " + name);
}
}
function timer(x, i)
{
x[i]();
if (i < x.length - 1) {
setTimeout(function () {
timer(x, i + 1);
}, 2000);
}
}
var x = [sayHello("Nakib"), sayHello("world")];
setTimeout(function () {
timer(x, 0);
}, 2000);

setTimeout needs a function without parameter. So you can wrap the recursive call to timer in an anonymous function to fix that:
window.setTimeout(function(){timer(x, i)}, 2000);
Also, the first line in your timer function, consisting only of x[i];, is useless, although it probably isn't the cause of your problem.

The setTimeout function takes a function as a parameter, you are executing the timer function before it is passed and since timer doesn't return anything, undefined is being passed to the timeout;
window.setTimeout(timer(x, i), 2000); // is the same as...
window.setTimeout(undefined, 2000);
It should be;
window.setTimeout(function() { timer(x, i) }, 2000); // or...
window.setTimeout(timer.bind(this, x, i), 2000);
I'm not sure if this is intentional, but you are doing the same thing with your array;
var x = [call("Nakib"), call2()];
This will execute the functions and their results will be stored in the array. Is this what you want?

overriding a javascript function's return statement

Assume I have a js function. From some other point in the program, I want to run its code, but not its return statement. In its place, I would like to run some other return statement that references the variables in the scope of the original function.
Is there a way to do this, other than loading up the function source, replacing the return, and using eval on the result? Minimal modification of the original is possible, though it should not affect the original's performance by adding e.g. an extra function call.

You could try something like this, but I'm not sure it meets your conditions.
Edit: Fixed to work in jsfiddle
// Modified to set all "shared" variables as "members" of the function.
var test = function() {
test.val = "one";
test.val2 = "two";
return 1;
}
// Using different result
function test2() {
test();
return test.val2;
}

Unless you're able to restructure your methods to accommodate a callback or introduce some other parameter-based logic-flow (not an option for 3rd party code), you're out of luck.
Here's a callback sample (fiddle, credit to dzejkej's answer)
function foo(callback) {
var x = 2;
// pass your values into the callback
return callback ? callback.call(this, x) : x * 2;
}
document.write(foo());
document.write("<hr/>");
// specify the parameters for your callback
document.write(foo(function(x){ return x * 4;}) );

You can introduce a callback function that will get called if available otherwise "standard" value will be returned.
function test(callback) {
// ...
return callback ? callback.call(this) : /* original value returned */ "xyz";
}
test(function() { /* "this" is same as in test() */ });
EDIT:
If you want to pass variables inside callback then you just list them in the .call() function.
Example:
function test(callback) {
var a = 4;
var b = 2;
// ...
return callback ? callback.call(this, a, b) : a * b;
}
test(); // 8
test(function(a, b) { return a + b; }); // 6
See this fiddle.

Provided that you would keep variables of the outer scope function within a single object, you could try something like the following:
function original(a, b, c, rep) {
var data = {};
// Do some fancy stuff but make sure to keep everything under data
data.a = a.replace(/foo/, 'bar');
...
if ( Object.prototype.toString.call(rep) === '[object Function]' )
return rep.call(data);
return data;
}
function replacement() {
return 'foo' + this.a;
}
// Now let's make use of both the original and the replacement ...
console.log(original('foo', x, y)); // => {a: "bar", b: ...}
console.log(original('foo', x, y, replacement)); // => {a: "foobar", b: ...}
Hope, it's what you where asking for.
cheers

I think you really misunderstand the concept of return statement. The return statement of a function will simply return a value, or an object, or undefined if there is no return parameter specified.
If all you're trying to do is execute a function but "not its return statement" than you would just invoke the function and not do anything with the returned value/object:
However, if what you mean is that you would like to execute a function but not execute the "parameter" to its return statement then that literally means to selectively execute an arbitrary portion of the body of a function. And as far as I know that is not possible (without using reflection to get the function definition, modify the definition, and then dynamically invoking the modified version - which you said you didn't want to do).