var number=str.replace(/^[^ 1-9]*|\d/g,'')；

Alarm (number);

Conventional description

The middle | means or, that is, as long as one of the conditions on both sides of it is met, it will be replaced by null.

The first indicates the beginning.

[1-9] means a number other than 1-9 (in [], it means none).

* indicates that the previous content can be none or one or more.

\D means non-number.

G is a global match, otherwise it is only matched (replaced) once.