Need help with a JavaScript regex

Question

I am allowing to make a new field in one of my web apps, to add a product.

Pushing add a product clones one of the inputs, and I set it to a blank value.

I need to update the name however. The name is in this format

<input type="text" name="product[0][0][3][title]" value="my product" id="input-AbGHtQS3" maxlength="150" />

I need to increment the last numerical index, that is the 3 in this example.

I wrote a regex to match the character, but I must be having a bad day, as I can't come up with something to increment that last number.

Here is my regex:

/^product\[\d+\]\[\d+\]\[(\d+)\]\[.+\]/

How could I increment that last number?

Answer 1

from: http://stackoverflow.com/questions/423107/use-regexp-to-match-a-parenthetical-number-then-increment-it

The replace method can take a function as its second argument. It gets the match (including submatches) and returns the replacement string. Others have already mentioned that the parentheses need to be escaped.

"Item Name (4)".replace(/\((\d+)\)/, function(fullMatch, n) {
    return "(" + (Number(n) + 1) + ")";
});

So,

*edit:

this should work

"product[0][0][3][title]".replace(/(^product\[\d+\]\[\d+\]\[)(\d+)(\]\[.+\])/, function(fullMatch, n, a, o) {
    return n + (Number(a) + 1) + o;
});

Answer 2

A more iterative approach:

r = /^(product\[\d+\]\[\d+\]\[)(\d+)(\]\[[a-z]+\])$/;
m = s.match(r);
if (!m) { /* do something smart; */ }
s.replace(r, "$1" + (Number(m[2]) + 1) + "$3");

I added a capture group at the head and tail of your regex. Then match, increment, and reassemble the string.

+1 for the match function on the regex though, I didn't know that trick.

Answer 3

Based on Andrew's answer, but corrected to return entire string:

"product[0][0][3][title]".replace (
    /^(product\[\d+\]\[\d+\]\[)(\d+)(\]\[.+\])/,
    function(fullMatch, pre, n, post) {
        return pre + (Number(n) + 1) + post;
    }
);