Function to validate URLs

validate_url.js

/**
VALIDATE URL
------------------------------------------------------
Requires punycode.js found at https://mths.be/punycode
to handle UTF-8. Has a very high true-positive rate, 
and low false-positive rate on this test-suite 
https://mathiasbynens.be/demo/url-regex
**/

function validate_url(link){

    link = link.trim()

    if (link.substring(0, 7) != "http://" && link.substring(0, 8) != "https://"){
        link = "http://" + link
    }

    url = new URL(link);

    link = url.protocol + "//" + punycode.toASCII(url.host + url.pathname + url.search) 

    var regexp = /^(?:http(?:s)?:\/\/)(?:(?:[\w:@_-]+\.)+[A-Za-z]+|(?:\d{1,3}\.){3}\d{1,3})(?::\d{1,4})?(?:[\/\w?#=&()_%-]+)?$/umi
    if (regexp.test(link)) {
        return link
    }else{
        return false;
    }
}