javascript数组和/或jquery $ .inArray（）和.splice（）

Question

I am working with an array that can have only 12 values in it; 1 through 12. These values can exist in any order. I need to go through the array and find the first unused value and then set it to a variable.

For example, if the array contains the values [1, 7, 2, 5, 10] I want to set the variable to 3 since it was the first unused number in numerical order. I am working with jQuery 1.9.1 and jQuery UI 1.10.1, but if this can be solved in plain javascript that is fine too!

Below is my code, which I know is wrong since it always sets the variable to 1. Note: tCounter is a global array used in several functions, so I do not want to modify the contents here. This is why I created tArray to splice values out of. Thanks for your help!

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

for (i = 1; i < 12; i++) {
    if (jQuery.inArray(i, tCounter)) {
        tArray.splice($.inArray(i, tArray), 1);
    }
}

if (tArray.length <= 0) {
    term = 1;
} else {
    term = tArray[0];
}

Answer 1

There are two errors that I can see in your current implementation.

First, your for loop indexing appears to be one off. In its current state, it will not check for the existence of the number 12, (due to your conditional i<12 ).

Second, your if statement actually evaluates to false when it should be true. If the index in the array is 0, (0 evaluates to false in Javascript), you should enter the statement. Taking what you have I would rewrite your code as follows:

  var i;
  var t; //this isn't used, perhaps it should be 'term'?

  for (i = 1; i < 13; i++) {
     // if we find a number that isn't in tCounter, we exit the loop.
     if (jQuery.inArray(i, tCounter) === -1) {
         term = i;
         break;
     }

     //sets term to null if all numbers are present in array.
     term = null;
  }

If your values were not the numbers 1-12 but rather arbitrary numbers, your idea of splicing values out of an array would work nicely, but as is, you really don't need the var tArray at all.

Sidenote: In an interesting comparison, it seems that if you are looking for the fastest implementation possible, you should use tCounter.indexOf(i) instead of jQuery.inArray(i, tCounter) , I wasn't sure which was faster, but this nifty test confirmed my suspicions.

Answer 2

A naive solution is to iterate from 1-12 and check for the existence of that value in the array. Like this:

var i;
for(i=1; i<12; i+=1) {
   if (tArray.indexOf(i) === -1) break;
}

term = i;