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());

Riz · Accepted Answer · 2012-07-19 10:22:24Z

2

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

answered Jul 19, 2012 at 10:22

Riz

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1 Comment

Riz Over a year ago

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

Esailija · Accepted Answer · 2012-07-19 10:22:29Z

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();
    }

answered Jul 19, 2012 at 10:22

Esailija

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Comments

Quentin · Accepted Answer · 2012-07-19 10:22:36Z

0

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);

answered Jul 19, 2012 at 10:22

Quentin

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