What numbers of an array add upto a given number

 For example, in an array like [1,2,3,4,5], what numbers add up to 9?

The answers are 4 and 5, of course.

The next question is, what are the different ways we can write this program by comparing time complexity.

function addUpto(array,weight)
{
    for(var i=0;i<array.length; i++)
    {
        for(var j=i+1; j<array.length; j++)
        {
            if(array[i]+array[j]==weight)
            {
                return [array[i],array[j]];
            }
        }
    }
return 'no matching';
}

//To execute the above code, 
addUpto([1,2,3,4,5],9); //output is [4,5]

Time complexity: O(n2)