How to get last occurrence with regex javascript?

One option could be to use a capturing group to match a word character or a hyphen. Your match will be in the first capturing group.

^.*?\/([\w-]+)\.html

That will match:

• ^ Start of the string
• .*? Match any character except a newline non greedy
• \/ Match /
• ([\w-]+) Capturing group to match 1+ times a wordcharacter of a hyphen
• \.html Match .html

Regex demo

const regex = /^.*?\/([\w-]+)\.html/;
const str = `https://www.aliexpress.com/category/200214036/women-watches.html?spm=2114.search0103.0.0.160b628cMC1npI&site=glo&SortType=total_tranpro_desc&g=y&needQuery=n&shipFromCountry=cn&tag=`;
console.log(str.match(regex)[1]);

Another option to match from the last occurence of the forward slash could be to match a forward slash and use a negative lookahead to check if there are no more forward slashes following. Then use a capturing group to match not a dot:

\/(?!.*\/)([^.]+)\.html

Regex demo

const regex = /\/(?!.*\/)([^.]+)\.html/;
const str = `https://www.aliexpress.com/category/200214036/women-watches.html?spm=2114.search0103.0.0.160b628cMC1npI&site=glo&SortType=total_tranpro_desc&g=y&needQuery=n&shipFromCountry=cn&tag=`;
console.log(str.match(regex)[1]);

Without using a regex, you might use the dom and split:

const str = `https://www.aliexpress.com/category/200214036/women-watches.html?spm=2114.search0103.0.0.160b628cMC1npI&site=glo&SortType=total_tranpro_desc&g=y&needQuery=n&shipFromCountry=cn&tag=`;
let elm = document.createElement("a");
elm.href = str;
let part = elm.pathname.split('/').pop().split('.')[0];
console.log(part);