How can I return a random value from an array?

Question

I'm using the jQuery validate plugin, and would like to return a random value on success.

Right now I'm trying to use:

     var success_message = new Array ();
     success_message[0] = "Good!";
     success_message[1] = "Ok!";
     success_message[2] = "Great!";
     success_message[3] = "Perfect!";
     success_message[4] = "Nice!";
     success_message[5] = "Awesome"; 
     var i = Math.floor(5 * Math.random())

Then where I need to output the value I use:

 $(document).ready(function(){
     var validator = $(".contactform").validate({
        success: function(label) {
           label.addClass("valid").text(success_message[i])
        }
     }); //end form validate code
 });

This selects a random value but uses the same value for each success message instead of selecting a different one for each field.

@Brandon - You should refrain from drastically changing the question once it's asked. The answers will now make much less sense to anyone finding this later since the question no longer matches the answers. — Nick Craver, Aug 05 '10 at 23:41
You're right I thought about that after I edited it. At the time I edited it it had no answers. — Brooke., Aug 06 '10 at 00:05

Nick Craver · Accepted Answer · 2010-08-05T23:48:01.983

91

You can store the messages array and calculate the message to show as you go, like this:

var messages = ["Good!", "Great!", "Awesome!", "Super!", "Nice!"];
function getMessage() {
   return messages[Math.floor(Math.random() * messages.length)];
}

Give it a try here, then just call getMessage in your .text() call, like this:

label.addClass("valid").text(getMessage());

edited Aug 05 '10 at 23:48

answered Aug 05 '10 at 23:35

Nick Craver

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This almost works but returns the same message for each field element. – Brooke. Aug 05 '10 at 23:45
@BandonRandon - I was under the impression you had just one, just a moment :) – Nick Craver Aug 05 '10 at 23:47
@BandonRandon - Updated to be random per-element, I would suggest that you may want to go a step further and remove the used message as well, so it can't be repeated. – Nick Craver Aug 05 '10 at 23:49
Sorry, I should had made that clear there is one for each form element. – Brooke. Aug 05 '10 at 23:49
@BandonRandon - No worries, give it a try now :) – Nick Craver Aug 05 '10 at 23:50
1

Great that works! Thank you, A few more questions, If I did want to make it not repeat how would I do that? Also because it's initializing on keyup It's regenerating with each keypress or mouse click. Can I use stop() or something to stop that? – Brooke. Aug 05 '10 at 23:57
@BandonRandon - You would have to do a full re-validation, actually I'm not sure how you'd handle it in your case, aside from looping through the current labels, which is fairly expensive. It will re-generate every time by default, you could try `if(label.text() == '') label.text(getMessage())`, see if that stops your unwanted label-changing. – Nick Craver Aug 06 '10 at 00:03
I think because it's adding the class of "valid" something like this should work `function successMessage() { if(!$("label").hasclass("valid")){ return messages[Math.floor(Math.random() * messages.length)]; } }` but it dosen't – Brooke. Aug 06 '10 at 00:51

score 7 · Answer 2 · answered Apr 22 '15 at 09:25

7

We can add Method to Array.

Array.prototype.getRandomVal = function(){
    return this[Math.floor(Math.random()*this.length)];
};

messages.getRandomVal();

answered Apr 22 '15 at 09:25

Rakesh Kumar

2,705
1
19
33

score 5 · Answer 3 · answered Aug 05 '10 at 23:36

function sucess() {
 message = ["Good!","Awesome!","Super!","Nice!","Great!"];
 return message[Math.floor(Math.random() * message.length)];
}

 $(document).ready(function(){
     var validator = $(".contactform").validate({ ...
              success: function(label) {
    label.addClass("valid").text(success());
 }
      }); //end form validate code
         });

score 1 · Answer 4 · answered Mar 10 '23 at 15:56

A concise way of choosing a random element of the array is to use bitwise OR instead of Math.floor(). This works because bitwise operations will cause the fractional part of the number to be discarded, which achieves exactly the same result as Math.floor(). Operator precedence means that the bitwise operation happens after the multiplication. Doing bitwise OR with zero leaves the original number unaffected, except that now the fractional part is gone.

const arr = ["Good!", "Great!", "Awesome!", "Super!", "Nice!"]

const randomElement = arr[Math.random() * arr.length | 0]

console.log(randomElement)

How can I return a random value from an array?

4 Answers4

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