Find first missing number in a sequence of numbers

Question

I am trying to figure out how to find the first missing number of a sequence of numbers like this (1,2,3,5,6,9,10,15)

I want to put the first missing number, #4, into an variable for later use but don't know how to do so?

I have tried this but this only gives me the last number:

var mynumbers=new Array(1,2,3,6,9,10);

for(var i = 1; i < 32; i++) {

    if(mynumbers[i] - mynumbers[i-1] != 1) {

        alert("First missing number id: "+mynumbers[i]);

        break;

    }

}

First of all it gives me the first number after an "hole" in the numbersequence, secondly it continues to alert all numbers comming after an "hole" if I don't insert an break. I only want the first missing number of an numbersequence from 1 - 32. How do i do so?

Hoping for help and thanks in advance ;-)

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Answer 1

How about this

var mynumbers = new Array(1,2,3,6,9,10);
var missing;

for(var i=1;i<=32;i++)
{    
   if(mynumbers[i-1] != i){
        missing = i;
        alert(missing);
        break;
   }
}

Find first missing number in a sequence of numbers

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