How to run a randomly selected function in JavaScript?

Question

I'm trying to run a random function but haven't quite figured it out:

<script>

function randomFrom(array) {return array[Math.floor(Math.random() * array.length)];}

function randomchords(){randomFrom(['poop()', 'poop2()', 'poop3()']);}               



function poop() { $(function() {ionian_c_vi() });  }                          

function poop2() {  $(function() {ionian_c_iii() }), $(function() {ionian_c_iv() });  }                      

function poop3() { $(function() {ionian_c_vi() }), $(function() {ionian_c_i() }), $(function() {ionian_c_ii() });  }  

</script>

and then:

<button onclick="randomchords()" >Get some random chords</button>

Am I on the right track?

Just stick some eval's in there and you'll be golden! +1 on the poop functions BTW. — adeneo
– adeneo, Commented May 21, 2012 at 22:31
It draws ukulele chords with Raphael! When it's done it will spit out random chord progressions. — jthomasbailey
– jthomasbailey, Commented May 21, 2012 at 22:39

VisioN · Accepted Answer · 2012-05-21 22:45:39Z

9

One option is to use window object:

function randomchords() {
    var func = randomFrom(['poop', 'poop2', 'poop3']);
    window[func]();
}

Pay attention that you should remove parentheses from function names in the array.

Another option is to remove quotes from the variant above and call functions directly:

function randomchords() {
    var func = randomFrom([poop, poop2, poop3]);
    (func)();
}

edited May 21, 2012 at 22:45

answered May 21, 2012 at 22:30

VisioN

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3 Comments

Bergi Over a year ago

...but maybe its better to store the function in their own object, not on the global one.

VisioN Over a year ago

@Bergi Possibly yes but the solution will be almost the same.

bobince Over a year ago

Why the strings? Why not just randomFrom([poop, poop2, poop3])()?

Aadaam · Accepted Answer · 2012-05-21 22:35:12Z

6

Functions are like values. You could say:

var myArray = [
    function(){
        ionian_c_vi();
    },
    function(){
        ionian_c_iii();
        ionian_c_iv()
    },
    function(){
        ionian_c_vi();
        ionian_c_i();
    }
];
function randomchords(){ 
     randomFrom(myArray).call();
}

For more info, look at http://www.yuiblog.com/blog/2010/02/24/video-crockonjs-3/ and/or read at https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Function/Call

Bookwise, read Javascript: The Good Parts (120 pages)

Helps learn JS outside jQuery :)

answered May 21, 2012 at 22:35

Aadaam

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2 Comments

bobince Over a year ago

Better! But the call is still superfluous, randomFrom(myArray)() is fine.

Aadaam Over a year ago

It is true that it's superfluous, it's more like a personal choice of style - it denotes that I expect something "callable". I use call or apply always when requesting function references.

Tharabas · Accepted Answer · 2012-05-22 05:49:35Z

1

You're quite close:

function foo() { ... }
function bar() { ... }
function baz() { ... }

These functions are defined to the global scope, which is usually window within a browser. You can access them via string by calling window['foo'] for example. That will return the foo function itself (not the value from execution).

function randomFrom(array) {
  return array[Math.floor(Math.random() * array.length)];
}

function randomchords() {
  // add the 'window' prefix here
  randomFrom(window['foo', 'bar', 'baz'])();
}

edited May 22, 2012 at 5:49

answered May 21, 2012 at 22:36

Tharabas

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2 Comments

Bergi Over a year ago

I would have upvoted this if you didn't tell that nonsense about Math.random().

Tharabas Over a year ago

D'oh, corrected my mistake after some reading. I thought Math.random() would be 0 <= x <= 1 but apparently is 0 <= x < 1 ... so forget about that being careful part :D

Répás · Accepted Answer · 2012-05-21 22:33:08Z

0

You can do this many way:

But the easiest i think to generate a random number, and call functions with case :)

$("button").click(function)
{
    var n = Math.floor(Math.random()*11);
    switch(n)
    {
        case: 0:
        Function0();
        break;

        case: 1:
        Function1();
        break;

        case: 2:
        Function2();
        break;

        ...

        case: 10:
        Function10();
        break;
}

With btn you can call

<button>Get some random chords</button>

answered May 21, 2012 at 22:33

Répás

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