ES6 filter an array with Regex

Question

I'm trying to filter an array that contains a bunch of urls. I need to return the urls that only contain the word "contact".

For example there is a link https://www.example.com/v1/contact-us/ca

This should be returned from the filter.

I tried this:

    const regex = new RegExp("/\bcontact\b", 'g' )     sites.links.filter((val) => {       console.log(regex.test(val.href))      }) 

It currently just sends back false through all the domains, when I know there is one domain that contains the word "contact".

Answer 1

Firstly new RegExp('/\bcontact\b', 'g'); is equivalent to /\/@contact@/g where the @ are backspace character (ASCII 08) ... clearly not what you want

So, you would do new RegExp('/\\bcontact\\b', 'g'); - this is equivalent to /\/\bcontact\b/g

However, the \\b after / is redundant

so ... down to /\/contact\b/g

Using string.match here as regex.test is misused. Below is the description

var sites = {      links: [         {href: 'https://www.example.com/v1/contact-us/ca'},         {href: 'https://www.example.com/v1/contact-us/au'},         {href: 'https://www.example.com/v1/contact-us/us'},         {href: 'https://www.example.com/v1/dontcontact-us/us'}     ] };  const regex = new RegExp('/contact\\b', 'g'); const matchedSites = sites.links.filter(({href}) => href.match(regex)); console.log(matchedSites); 

The next problem is using the ONE regex multiple times in a regexp.test with g flag. With each call, it will look from the next indexOf previous found substring and with consecutive calls on a same-type string, it basically will return true, false, true, false.

If you want to use regex.test, then don't re-use the same regex unless you know the consequences of doing so or do not use g flag (which here you do not need)

var sites = {       links: [          {href: 'https://www.example.com/v1/contact-us/ca'},          {href: 'https://www.example.com/v1/contact-us/au'},          {href: 'https://www.example.com/v1/contact-us/us'},          {href: 'https://www.example.com/v1/dontcontact-us/us'}      ]  };    const regex = new RegExp('/contact\\b', 'g');  const correctRegex = new RegExp('/contact\\b');    const matchedSitesFailed = sites.links.filter(({href}) => regex.test(href));  const matchedSitesSuccess = sites.links.filter(({href}) => new RegExp('/contact\\b', 'g').test(href));  const matchedSitesSuccess2 = sites.links.filter(({href}) => correctRegex.test(href));    console.log('failed returns:', matchedSitesFailed.length);  console.log('success returns:', matchedSitesSuccess.length);  console.log('success returns 2:', matchedSitesSuccess2.length);