function removeByValue(arr, val) {
  for(var i=0; i<arr.length; i++) {
    if(arr[i] == val) {
      arr.splice(i, 1);
      break;
    }
  }
}
var somearray = ["mon", "tue", "wed", "thur"]
removeByValue(somearray, "tue");

// somearray will now have "mon", "wed", "thur"