Pass a JavaScript function as parameter

How do I pass a function as a parameter without the function executing in the "parent" function or using eval() ? (Since I've read that it's insecure.)

I have this:

addContact(entityId, refreshContactList());

It works, but the problem is that refreshContactList fires when the function is called, rather than when it's used in the function.

I could get around it using eval() , but it's not the best practice, according to what I've read. How can I pass a function as a parameter in JavaScript?

---

You just need to remove the parenthesis:

addContact(entityId, refreshContactList);

This then passes the function without executing it first.

Here is an example:

function addContact(id, refreshCallback) {
    refreshCallback();
    // You can also pass arguments if you need to
    // refreshCallback(id);
}

function refreshContactList() {
    alert('Hello World');
}

addContact(1, refreshContactList);

---

If you want to pass a function, just reference it by name without the parentheses:

function foo(x) {
    alert(x);
}
function bar(func) {
    func("Hello World!");
}

//alerts "Hello World!"
bar(foo);

But sometimes you might want to pass a function with arguments included, but not have it called until the callback is invoked. To do this, when calling it, just wrap it in an anonymous function, like this:

function foo(x) {
   alert(x);
}
function bar(func) {
   func();
}

//alerts "Hello World!" (from within bar AFTER being passed)
bar(function(){ foo("Hello World!") });

If you prefer, you could also use the apply function and have a third parameter that is an array of the arguments, like such:

function eat(food1, food2)
{
    alert("I like to eat " + food1 + " and " + food2 );
}
function myFunc(callback, args)
{
    //do stuff
    //...
    //execute callback when finished
    callback.apply(this, args);
}

//alerts "I like to eat pickles and peanut butter"
myFunc(eat, ["pickles", "peanut butter"]); 

---

Example 1:

funct("z", function (x) { return x; });

function funct(a, foo){
    foo(a) // this will return a
}

Example 2:

function foodemo(value){
    return 'hello '+value;
}

function funct(a, foo){
    alert(foo(a));
}

//call funct    
funct('world!',foodemo); //=> 'hello world!'

look at this

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