Please refer below code.
for (var i = 0; i < elements.length; i++)
{
//var element = elements[Math.floor(Math.random()*elements.length)];
this.animateSymbol(elements[Math.floor(Math.random()*elements.length)]);
}
elements array contains list of svg elements(circle/path/ellipse etc). I want to select the random element from elements array.
it's return the same element in some cases I want to select the element randomly no need to select the same element again. Need to select different element from that array.
What's the problem ? Why its returning same index and same element ?
Thanks,
Siva
Please refer below code.
for (var i = 0; i < elements.length; i++)
{
//var element = elements[Math.floor(Math.random()*elements.length)];
this.animateSymbol(elements[Math.floor(Math.random()*elements.length)]);
}
elements array contains list of svg elements(circle/path/ellipse etc). I want to select the random element from elements array.
it's return the same element in some cases I want to select the element randomly no need to select the same element again. Need to select different element from that array.
What's the problem ? Why its returning same index and same element ?
Thanks,
Siva
Share Improve this question edited Jun 11, 2013 at 9:31 Rakesh Shetty 4,5788 gold badges42 silver badges81 bronze badges asked Jun 11, 2013 at 9:22 SivaRajiniSivaRajini 7,37522 gold badges84 silver badges129 bronze badges 2- 2 Nothing says the random number can't be the same as a previous random. – Kevin Bowersox Commented Jun 11, 2013 at 9:29
- are you sure elements contains more than one element? Do a console.log(elements.length) . – Stefan Commented Jun 11, 2013 at 9:30
5 Answers
Reset to default 8Random numbers are random. There's no guarantee you won't get the same random number twice. In fact, when you convert the random numbers to a limited range of integers, it's quite likely you will get the same number twice.
You can fix this by copying the array and then each time you get a value from the array, remove it. Let's also break out the code that generates the random index as a separate function; it's handy in other situations too:
// Return a random integer >= 0 and < n
function randomInt( n ) {
return Math.floor( Math.random() * n );
}
var copy = elements.slice();
while( copy.length ) {
var index = randomInt( copy.length );
this.animateSymbol( copy[index] );
copy.splice( index, 1 );
}
And just for fun, here's another way you could code that loop:
var copy = elements.slice();
while( copy.length ) {
var index = randomInt( copy.length );
this.animateSymbol( copy.splice( index, 1 )[0] );
}
Either one does the same thing. I kind of like the step by step approach for clarity, but it can be quite handy that the .splice() method returns an array of the element(s) you delete.
Here's a version of the code you can paste into the JavaScript console to test:
// Return a random integer >= 0 and < n
function randomInt( n ) {
return Math.floor( Math.random() * n );
}
var elements = [ 'a', 'b', 'c', 'd', 'e' ];
var copy = elements.slice();
while( copy.length ) {
var index = randomInt( copy.length );
console.log( copy.splice( index, 1 )[0] );
}
console.log( 'Done' );
It's also worth a look at Xotic750's answer. It uses the Fisher-Yates shuffle which randomizes an array in place. This would likely be more efficient for a very lengthy array.
So what you want is akin to a deck of cards, you shuffle them and take them one by one and therefore they are never repeated.
I would use something like the following for your problem, uses a standard Fisher-Yates shuffle.
function shuffle(obj) {
var i = obj.length;
var rnd, tmp;
while (i) {
rnd = Math.floor(Math.random() * i);
i -= 1;
tmp = obj[i];
obj[i] = obj[rnd];
obj[rnd] = tmp;
}
return obj;
}
var elements = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
var randomised = elements.slice();
shuffle(randomised);
randomised.forEach(function(element) {
console.log(element);
});It is because you are using random there is no assurance that same number will not be repeated.
In your case I would suggest you to use some sort of shuffle to create a random order array.
You can find such method here
Try capturing the random numbers generated and checking that you are not using them over again.
Here is a quick object I created for this purpose:
function PersistentRandom(exclusiveUpperBounds){
this.spent = [];
this.bounds = exclusiveUpperBounds;
}
PersistentRandom.prototype.getValue = function(){
if(this.spent.length != this.bounds -1){
var tmp = Math.floor(Math.random()* this.bounds);
if(this.spent.indexOf(tmp) == -1){
this.spent.push(tmp);
return tmp;
}else{
return this.getValue();
}
}else{
//If all numbers are used reset and start again
this.spent = [];
return this.getValue();
}
};
//Usage
var pr = new PersistentRandom(11);
var x = 0;
while(x < 15){
console.log(pr.getValue());
x++;
}
Working Example http://jsfiddle/zasdj/
So you want a random element each time? but never the same element twice?
try this:
for (var i = 0; i < elements.length; i++) {
//var element = elements[Math.floor(Math.random()*elements.length)];
var index = Math.floor(Math.random()*elements.length);
this.animateSymbol(elements[index]);
elements.splice(index, 1);
}
this will remove the item from array once it has been selected