The trick here is go through the string character by character and see what is a number or not. When you encounter a number, add them up until you get to the next non-number character. Once you’re at the end, sum up all the numbers.

We had quite a few submissions here, and the shortest one uses Regular Expressions for this.

For example, this JavaScript solution is more or less a one-liner:

let solution = 0;
puzzle.split(/\D/).forEach(
    v => { solution += +v} 
);

• You define solution as 0
• you split the puzzle string at any numeric string
• you loop over the results and add the integer value to solution (+v is shorter for parseInt(v,10))

Other submissions:

• The same approach in PHP
• A JavaScript solution by Phil Nash using match()
• A looping JavaScript solution not using RegEx
• A JavaScript solution using reduce()