Question

120

ES6 filter an array with Regex

rated 0 times [ 121] [ 1] / answers: 1 / hits: 84435 / 7 Years ago, mon, october 30, 2017, 12:00:00

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(/bcontactb, '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.

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yosefleod

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answered 7 Years ago yasmeeng · Accepted Answer

Firstly new RegExp('/bcontactb', '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 //bcontactb/g

However, the \b after / is redundant

so ... down to //contactb/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);