Find non-negative integers
There’s a string of integer numbers.
Create a regexp that looks for only non-negative ones (zero is allowed).
An example of use:
let regexp = /your regexp/g; let str = "0 12 -5 123 -18"; alert( str.match(regexp) ); // 0, 12, 123
The regexp for an integer number is
We can exclude negatives by prepending it with the negative lookahead:
Although, if we try it now, we may notice one more “extra” result:
As you can see, it matches
-18. To exclude it, we need to ensure that the regexp starts matching a number not from the middle of another (non-matching) number.
We can do it by specifying another negative lookbehind:
(?<!\d) ensures that a match does not start after another digit, just what we need.
We can also join them into a single lookbehind here: