javascript - Decrease the probability of getting random item from array same as previous one -

say, i've got array like

var arr = [1,2,3,4,5,6,7,8,9,10,11,12]; 

and wanna random array item, later re-randomize current item. efficient way exclude or reduce chance of getting same item once again?

does stuff help:

current != arr[math.floor(math.random() * 12)] ? current = arr[math.floor(math.random() * 12)] : arr[math.floor(math.random() * 12)]; 

i mean, recalculate random array index each time or link same value? better way?

if can keep array unsorted: (if not, can use array contains indices of elements in first array)

var array = [ ... ]; var len = array.length;  function getrandomitem(){     if (len <= 0) len = array.length;     var item = math.floor(math.random()*len--);     var x = array[item];     array[item] = array[len];     array[len] = x;     return array[len]; } 

idea behind exclude dispatched items placing them outside of item fetching range. function getrandomitem() not return same item twice until other elements returned.

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following modification prevent function return same element returned during previous call, requested.

var array = [ 3, 1, 4, 5, 9, 2, 6, 8, 7 ];  var len = array.length-1;    function getrandomitem(){      if (len == 0) return array[0];      var item = math.floor(math.random()*len);      var x = array[item];      array[item] = array[len];      array[len] = x;      return array[len];  }    document.write("starting array: " + array + "<br/>");  document.write("selected value: " + getrandomitem() + "<br/>");  document.write("resulting array: " + array);

also see fisher–yates shuffle