JAVASCRIPT

Check if a JavaScript string is a URL

function isValidURL(string) {
  var res = string.match(/(http(s)?://.)?(www.)?[-a-zA-Z0-9@:%._+~#=]{2,256}.[a-z]{2,6}([-a-zA-Z0-9@:%_+.~#?&//=]*)/g);
  return (res !== null)
};

var testCase1 = "http://en.wikipedia.org/wiki/Procter_&_Gamble";

alert(isValidURL(testCase1)); 

javascript url check

const isAbsoluteUrl = url => /^[a-z][a-z0-9+.-]*:/.test(url);

// Example
isAbsoluteUrl('https://1loc.dev');          // true
isAbsoluteUrl('https://1loc.dev/foo/bar');  // true
isAbsoluteUrl('1loc.dev');                  // false
isAbsoluteUrl('//1loc.dev'); 

javascript determine if string is valid url

function isValidHttpUrl(string) {
  let url;
  
  try {
    url = new URL(string);
  } catch (_) {
    return false;  
  }

  return url.protocol === "http:" || url.protocol === "https:";
}

check-if-a-javascript-string-is-a-url

  const isUrl = string => {
      try { return Boolean(new URL(string)); }
      catch(e){ return false; }
  }