Run functions randomly

Question

I have an array that includes some functions and it looks like this:

var all_questions = [
    show_question(1, 1),
    show_question(2, 1),
    show_question(3, 1),
];

I would like to run those functions into that array randomly. How can I do that?

All functions will be executed at the time when the array is getting created — Rajaprabhu Aravindasamy, Jul 28 '16 at 15:23
To extend @RajaprabhuAravindasamy's comment - the parenthesis at the end of the function name is what actually "calls" the function. — Lix, Jul 28 '16 at 15:24
Can you elaborate what you mean by "run those functions into that array randomly". Do you mean you want to run only one of them? Or run them all in a random order? Or something else? — Darren H, Jul 28 '16 at 15:27

score 6 · Answer 1 · edited May 23 '17 at 12:34

Firstly you need to wrap those functions in anonymous functions, otherwise they will be called immediately. From there you can get a random element from the array and call it, like this:

var all_questions = [
    function() { show_question(1, 1) },
    function() { show_question(2, 1) },
    function() { show_question(3, 1) },
];

all_questions[Math.floor(Math.random() * all_questions.length)]();

function show_question(a, b) {
  console.log(a, b);
}

Note that you could improve the logic by just randomising the first parameter of the function only, instead of storing function references in an array:

function show_question(a, b) {
  console.log(a, b);
}

var rnd = Math.floor(Math.random() * 3) + 1;
show_question(rnd, 1);

It's most likely for posting an answer on a very poorly written question. — takendarkk, Jul 28 '16 at 18:53

Lix · Answer 2 · 2016-07-28T18:51:56.800

2

If you are calling the same function with different arguments, I would say it's a better option to select the arguments randomly instead of the function.

var args = [
  [1,2],
  [1,3],
  [1,4],
  ...
]

// Get a random element from the array
// http://stackoverflow.com/a/4550514/558021
var randomArgs = args[ Math.floor( Math.random()*args.length) ];

show_question.apply( this, randomArgs );

The apply function is used here because of the way it passes arguments to the target function. When you use apply to execute a function, the arguments you want to pass to the function are provided in an array and then split into individual arguments when passed to the target function.

edited Jul 28 '16 at 18:51

answered Jul 28 '16 at 15:28

Lix

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You could use `show_question.apply(randomArgs)` and the OP wouldn't need to amend the function at all. – Rory McCrossan Jul 28 '16 at 15:31
I considered that but in the end chose this approach as I felt it would better suite the competence level of this question. – Lix Jul 28 '16 at 15:35
1

I can understand that, although IMO it's better to bring someone up to your level instead of catering to theirs. – Rory McCrossan Jul 28 '16 at 16:05

score 0 · Answer 3 · edited Jul 28 '16 at 15:45

0

something like

var all_questions = [
    function() show_question(1, 1),
    function() show_question(2, 1),
    function() show_question(3, 1),
];
var x = Math.floor((Math.random() * 3) + 1);
// do something you want
    all_questions[x];

edited Jul 28 '16 at 15:45

Liam

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answered Jul 28 '16 at 15:26

brad

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Just like in the original question, the functions will be called while you are defining the array. – Lix Jul 28 '16 at 15:37
@liam - did you notice that you removed a portion of the code sample that was provided? – Lix Jul 28 '16 at 15:43
hmm, not on purpose @lix. Edited to do what I actually meant to do, appologies – Liam Jul 28 '16 at 15:46
1

@liam - no worries, just wanted to give you a heads up – Lix Jul 28 '16 at 15:47

score 0 · Answer 4 · answered Jul 28 '16 at 15:50

You can do like this;

var allQuestions = [
                    showQuestion.bind(this, 1, 1),
                    showQuestion.bind(this, 2, 1),
                    showQuestion.bind(this, 3, 1),
                   ],
 displayQuestion = allQuestions[~~(Math.random()*allQuestions.length)];

Run functions randomly

4 Answers4