pass functions as a parameter in JavaScript

Question

How do I pass functions as a parameter in JavaScript.

In the code below if I call whatMustHappen (TWO(),ONE()) I want to them to fall in the sequence of the x and the y on the whatMustHappen function.

Right now it fires as it sees it in the parameter.

var ONE = function() {
 alert("ONE");
}
var TWO = function() {
 alert("TWO");
}
var THREE = function() {
 alert("THREE");
}
var whatMustHappen = function(x, y) {
 y;
 x;
}
whatMustHappen(TWO(), null);
whatMustHappen(TWO(), ONE());

Answer 1

var whatMustHappen = function(x, y) {
 if (y) y();
 if (x) x();
 }
whatMustHappen(TWO, null);
whatMustHappen(TWO, ONE);

• Riz: which error and why ? due to null ? OP should take care of that. Updated my answer anyway.

Answer 2

() invokes a function and returns its result. To pass a function, you simply pass it like any other variable:

whatMustHappen(TWO, ONE);

In whatMustHappen function, you can then call them:

var whatMustHappen = function(x, y) {
 if( y ) y();
 if( x ) x();
 }

Answer 3

If you want to pass a function, don't call it (with (args)).

function foo () {
 alert("foo");
}
function bar (arg) {
 alert("Function passed: " + arg);
 arg();
}
bar(foo);