Develop Reference

Why does the same single-use regex behave differently in two platforms?

I'm attempting to validate an RFC (Mexican tax id) code in a form with JS and JQuery. I only require to validate whether the following Regex match returns null:
function validateRFC(rfc) {
const rgxFisica = "^(([A-ZÑ&]{4})([0-9]{2})([0][13578]|[1][02])(([0][1-9]|[12][\\d])|[3][01])([A-Z0-9]{3}))|" +
"(([A-ZÑ&]{4})([0-9]{2})([0][13456789]|[1][012])(([0][1-9]|[12][\\d])|[3][0])([A-Z0-9]{3}))|" +
"(([A-ZÑ&]{4})([02468][048]|[13579][26])[0][2]([0][1-9]|[12][\\d])([A-Z0-9]{3}))|" +
"(([A-ZÑ&]{4})([0-9]{2})[0][2]([0][1-9]|[1][0-9]|[2][0-8])([A-Z0-9]{3}))$";
return rfc.match(rgxFisica) != null
}
const foo = validateRFC("XXXX901212UDX");
console.log(foo);
The pattern is basically XXXXYYMMDDYYY where X must be a letter, YMD are date values and Y can be any alphanumeric character.
I did a small unit test on codepen with my real id and it works. However, when testing it in my test environment it always returns null. Here's a screenshot. In case it matters, I'm rendering the entire page with Flask in Python 3.7, and the validation is inside document.ready
Is it possible that my Javascript is interpreting regular expressions differently?
EDIT:
It seems the embedded snippet also returns true. I'm using VS2019 16.3.5, Python 16.3.19252.1 in a Python 3.7 64-bit environment.

In some cases of javascript, like ECMAScript, if the match fails, then the call rfc.match(rgxFisica) will return an array. If the match passes, it will return a boolean true.
see example (https://jsfiddle.net/coq3Lugw/):
function validateRFC(rfc) {
const rgxFisica = "^(([A-ZÑ&]{4})([0-9]{2})([0][13578]|[1][02])(([0][1-9]|[12][\\d])|[3][01])([A-Z0-9]{3}))|" +
"(([A-ZÑ&]{4})([0-9]{2})([0][13456789]|[1][012])(([0][1-9]|[12][\\d])|[3][0])([A-Z0-9]{3}))|" +
"(([A-ZÑ&]{4})([02468][048]|[13579][26])[0][2]([0][1-9]|[12][\\d])([A-Z0-9]{3}))|" +
"(([A-ZÑ&]{4})([0-9]{2})[0][2]([0][1-9]|[1][0-9]|[2][0-8])([A-Z0-9]{3}))$";
console.log(rfc.match(rgxFisica))
console.log("hello 0670 world".match(rgxFisica))
return rfc.match(rgxFisica) != null
}
const foo = validateRFC("XXXX901212UDX");
//console.log(foo);
what I would do is set an if-then statement and return that way:
function validateRFC(rfc) {
const rgxFisica = "^(([A-ZÑ&]{4})([0-9]{2})([0][13578]|[1][02])(([0][1-9]|[12][\\d])|[3][01])([A-Z0-9]{3}))|" +
"(([A-ZÑ&]{4})([0-9]{2})([0][13456789]|[1][012])(([0][1-9]|[12][\\d])|[3][0])([A-Z0-9]{3}))|" +
"(([A-ZÑ&]{4})([02468][048]|[13579][26])[0][2]([0][1-9]|[12][\\d])([A-Z0-9]{3}))|" +
"(([A-ZÑ&]{4})([0-9]{2})[0][2]([0][1-9]|[1][0-9]|[2][0-8])([A-Z0-9]{3}))$";
if (rfc.match(rgxFisica)) == null{
return True
} else {
return False
}
}
const foo = validateRFC("XXXX901212UDX");
//console.log(foo);
An example of a TRUE regex match:
function validateRFC(rfc) {
const rgxFisica = "^(([A-ZÑ&]{4})([0-9]{2})([0][13578]|[1][02])(([0][1-9]|[12][\\d])|[3][01])([A-Z0-9]{3}))|" +
"(([A-ZÑ&]{4})([0-9]{2})([0][13456789]|[1][012])(([0][1-9]|[12][\\d])|[3][0])([A-Z0-9]{3}))|" +
"(([A-ZÑ&]{4})([02468][048]|[13579][26])[0][2]([0][1-9]|[12][\\d])([A-Z0-9]{3}))|" +
"(([A-ZÑ&]{4})([0-9]{2})[0][2]([0][1-9]|[1][0-9]|[2][0-8])([A-Z0-9]{3}))$";
console.log(rfc.match(rgxFisica));
if (rfc.match(rgxFisica) == null){
return true
} else{
return false
}
}
const foo = validateRFC("hello 0670 world");
console.log(foo);

How transcribe remove number custom function Excel VBA function to Google Sheets Google Script (Javascript)

I need to transcribe a VBA script to Javascript but i got stuck in the java part
The main meaning is to remove numbers from a text like "texthere 123456789"
My VBA code is:
Function RemoveNum(Txt As String) As String
With CreateObject("VBScript.RegExp")
.Global = True
.Pattern = "[0-9]"
RemoveNum = .Replace(Txt, "")
End With
End Function
My Javascript attempt was:
function RemoveNumbers(RemoveNumbers) {
var RemoveNumbers;
//var str = RemoveNumbers.toString();
var str = RemoveNumbers;
str.Value.replace(/[0-9]/g, '');
}
Or even:
function rn(remvnum) {
var str = remvnum;
var n = str.toString();
var res = n.replace(/[0-9]/gmi, '');
}
What does stop me reaching the result is, the .Replace function needs to be string content otherwise will return error of undefined value, also I can't convert toString because it returns error of undefined value.
This example bellow works well as the name of the function is written in the Google Sheet cell as a custom function, but I didn't achieve the remove number desire:
function styleHyphenFormat(propertyName) {
function upperToHyphenLower(match, offset, string) {
return (offset ? '-' : '') + match.toLowerCase();
}
return propertyName.replace(/[A-Z]/g, upperToHyphenLower);
}
Does someone knows what I did wrong?
Thanks in advance.

Try removeNumbers = removeNumbers.replace(/[0-9]/g, ''); or set a new var like noNums = removeNumbers.replace(/[0-9]/g, '');

You just need to return the replaced value:
function rn(remvnum) {
//var str = remvnum;
//var n = str.toString();
var res = remvnum.toString().replace(/[0-9]/gmi, '');
return res; //Added
}
Google sheets supports regex(re2) as a built-in function unlike excel. So, You don't need macros. Even if you want a global replace, The Find and replace menu works well with regex.
=REGEXREPLACE(A2,"\d",)
or
=ARRAYFORMULA(REGEXREPLACE(A2:A5,"\d",))
\d is digit(==[0-9])

Validate variable javascript

I need to validate some user input with javascript. I need to check that their entry (value) is of the correct type (type).
I need my regex pattern to make sure values only contain numbers and nothing else, except measurment types can also contain decimal points.
What is the correct way to do this? My way seems like it may be, but i am guessing. In any case, something is wrong with my regular expression patterns as it is throwing the error stated in the code comment.
Here is my code:
function validateInput(value, type) {
console.log(value);
if(type === "Integer"){
var patt = new RegExp("^\D", i);
}
else if(type === "Measurement"){
var patt = new RegExp("^\D", i); //Uncaught SyntaxError: Invalid flags supplied to RegExp constructor '2'
}
else{
return true;
}
if(patt.test(value)){
return false;
}
else{
return true;
}
}
function sendObs() {
RID = $("#oid").val();
console.log(RID);
var children = $("#abc").children();
var xmlString = "<root><rid>" + RID + "</rid>";
for(i=0; i < children.length; i++){
var value = children[i].children[0].value;
var type = children[i].children[0].id;
var validationResult = validateInput(value, type);
if(!validationResult){ //calling the validation method here
alert("invalid entry");
return;
}
var code = children[i].children[0].className;
xmlString += '<question><code>' + code + '</code><value>' + value + '</value></question>'
}
xmlString +='</root>'
console.log(xmlString);
data = $.parseXML(xmlString);
console.log(data);
//send it here
}

Instead of using regular expressions, you could just call parseInt() and parseFloat().
On top of converting your strings to workable numbers, both functions return NaN if the input is invalid.
number = parseFloat(string)
if (isNaN(number)) {
# `string` is invalid
}

Testing against a string/object

I have a JSON-encoded PHP array:
<script>
var registeredEmails = <?php echo(json_encode($emails)); ?>;
</script>
To check that this works, I do this:
console.log(registeredEmails);
// this outputs: ["john#domain.com", "mary#domain.com"]
And now I would like to iterate through that JSON and test a certain string against all the strings it contains.
for (var email in registeredEmails) {
if (registeredEmails.hasOwnProperty(email)) {
var duplicate = registeredEmails[email];
console.log(duplicate + ' is typeof: ' + typeof(duplicate));
// this outputs: john#domain.com is typeof: string
// $(this).val() is a string from somewhere else
if (duplicate.test($(this).val())) {
// we found a match
};
}
}
As I understand it, the test() method tests for matches on strings. I've tested to make sure that my variable duplicate is a string, but apparently it's still an object. I'm given the following JS error:
Uncaught TypeError: Object john#domain.com has no method 'test'
Why is that?

test() is a method of the RegEx object, not String.
Your best bet would probably be to use String.search() instead. You could also probably use String.indexOf() if you're not trying to use Regular Expression matching.

Although you are using json_encode your console output looks like an array to me. If that is the case then maybe you can use the following:
var found = find_match( registeredEmails, $(this).val() );
if( found ) {
// found a match
}
function find_match(array, string) {
for( var i = 0, len = array.length; i < len ; i++ ) {
if( array[i].indexOf( string ) > -1 ) return true;
}
return false;
}​
Fiddle here

Trying to Validate URL Using JavaScript

I want to validate a URL and display message. Below is my code:
$("#pageUrl").keydown(function(){
$(".status").show();
var url = $("#pageUrl").val();
if(isValidURL(url)){
$.ajax({
type: "POST",
url: "demo.php",
data: "pageUrl="+ url,
success: function(msg){
if(msg == 1 ){
$(".status").html('<img src="images/success.gif"/><span><strong>SiteID:</strong>12345678901234456</span>');
}else{
$(".status").html('<img src="images/failure.gif"/>');
}
}
});
}else{
$(".status").html('<img src="images/failure.gif"/>');
}
});
function isValidURL(url){
var RegExp = /(ftp|http|https):\/\/(\w+:{0,1}\w*#)?(\S+)(:[0-9]+)?(\/|\/([\w#!:.?+=&%#!\-\/]))?/;
if(RegExp.test(url)){
return true;
}else{
return false;
}
}
My problem is now it will show an error message even when entering a proper URL until it matches regular expression, and it return true even if the URL is something like "http://wwww".
I appreciate your suggestions.

Someone mentioned the Jquery Validation plugin, seems overkill if you just want to validate the url, here is the line of regex from the plugin:
return this.optional(element) || /^(https?|ftp):\/\/(((([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(%[\da-f]{2})|[!\$&'\(\)\*\+,;=]|:)*#)?(((\d|[1-9]\d|1\d\d|2[0-4]\d|25[0-5])\.(\d|[1-9]\d|1\d\d|2[0-4]\d|25[0-5])\.(\d|[1-9]\d|1\d\d|2[0-4]\d|25[0-5])\.(\d|[1-9]\d|1\d\d|2[0-4]\d|25[0-5]))|((([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])*([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])))\.)+(([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])*([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])))\.?)(:\d*)?)(\/((([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(%[\da-f]{2})|[!\$&'\(\)\*\+,;=]|:|#)+(\/(([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(%[\da-f]{2})|[!\$&'\(\)\*\+,;=]|:|#)*)*)?)?(\?((([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(%[\da-f]{2})|[!\$&'\(\)\*\+,;=]|:|#)|[\uE000-\uF8FF]|\/|\?)*)?(\#((([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(%[\da-f]{2})|[!\$&'\(\)\*\+,;=]|:|#)|\/|\?)*)?$/i.test(value);
Here is where they got it from: http://projects.scottsplayground.com/iri/
Pointed out by #nhahtdh This has been updated to:
// Copyright (c) 2010-2013 Diego Perini, MIT licensed
// https://gist.github.com/dperini/729294
// see also https://mathiasbynens.be/demo/url-regex
// modified to allow protocol-relative URLs
return this.optional( element ) || /^(?:(?:(?:https?|ftp):)?\/\/)(?:\S+(?::\S*)?#)?(?:(?!(?:10|127)(?:\.\d{1,3}){3})(?!(?:169\.254|192\.168)(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-z\u00a1-\uffff0-9]-*)*[a-z\u00a1-\uffff0-9]+)(?:\.(?:[a-z\u00a1-\uffff0-9]-*)*[a-z\u00a1-\uffff0-9]+)*(?:\.(?:[a-z\u00a1-\uffff]{2,})).?)(?::\d{2,5})?(?:[/?#]\S*)?$/i.test( value );
source: https://github.com/jzaefferer/jquery-validation/blob/c1db10a34c0847c28a5bd30e3ee1117e137ca834/src/core.js#L1349

It's not practical to parse URLs using regex. A full implementation of the RFC1738 rules would result in an enormously long regex (assuming it's even possible). Certainly your current expression fails many valid URLs, and passes invalid ones.
Instead:
a. use a proper URL parser that actually follows the real rules. (I don't know of one for JavaScript; it would probably be overkill. You could do it on the server side though). Or,
b. just trim away any leading or trailing spaces, then check it has one of your preferred schemes on the front (typically ‘http://’ or ‘https://’), and leave it at that. Or,
c. attempt to use the URL and see what lies at the end, for example by sending it am HTTP HEAD request from the server-side. If you get a 404 or connection error, it's probably wrong.
it return true even if url is something like "http://wwww".
Well, that is indeed a perfectly valid URL.
If you want to check whether a hostname such as ‘wwww’ actually exists, you have no choice but to look it up in the DNS. Again, this would be server-side code.

function validateURL(textval) {
var urlregex = /^(https?|ftp):\/\/([a-zA-Z0-9.-]+(:[a-zA-Z0-9.&%$-]+)*#)*((25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]?)(\.(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])){3}|([a-zA-Z0-9-]+\.)*[a-zA-Z0-9-]+\.(com|edu|gov|int|mil|net|org|biz|arpa|info|name|pro|aero|coop|museum|[a-zA-Z]{2}))(:[0-9]+)*(\/($|[a-zA-Z0-9.,?'\\+&%$#=~_-]+))*$/;
return urlregex.test(textval);
}
This can return true for URLs like:
http://stackoverflow.com/questions/1303872/url-validation-using-javascript
or:
http://regexlib.com/DisplayPatterns.aspx?cattabindex=1&categoryId=2

I written also a URL validation function base on rfc1738 and rfc3986 to check http and https urls. I try to hold this modular, so it can be better maintained and adapted to own requirements.
The RegExp in one line is show at end of this post.
The RegExp accept HTTP and HTTPS URLs with some international domain or IPv4 number. IPv6 is not supported yet.
window.isValidURL = (function() {// wrapped in self calling function to prevent global pollution
//URL pattern based on rfc1738 and rfc3986
var rg_pctEncoded = "%[0-9a-fA-F]{2}";
var rg_protocol = "(http|https):\\/\\/";
var rg_userinfo = "([a-zA-Z0-9$\\-_.+!*'(),;:&=]|" + rg_pctEncoded + ")+" + "#";
var rg_decOctet = "(25[0-5]|2[0-4][0-9]|[0-1][0-9][0-9]|[1-9][0-9]|[0-9])"; // 0-255
var rg_ipv4address = "(" + rg_decOctet + "(\\." + rg_decOctet + "){3}" + ")";
var rg_hostname = "([a-zA-Z0-9\\-\\u00C0-\\u017F]+\\.)+([a-zA-Z]{2,})";
var rg_port = "[0-9]+";
var rg_hostport = "(" + rg_ipv4address + "|localhost|" + rg_hostname + ")(:" + rg_port + ")?";
// chars sets
// safe = "$" | "-" | "_" | "." | "+"
// extra = "!" | "*" | "'" | "(" | ")" | ","
// hsegment = *[ alpha | digit | safe | extra | ";" | ":" | "#" | "&" | "=" | escape ]
var rg_pchar = "a-zA-Z0-9$\\-_.+!*'(),;:#&=";
var rg_segment = "([" + rg_pchar + "]|" + rg_pctEncoded + ")*";
var rg_path = rg_segment + "(\\/" + rg_segment + ")*";
var rg_query = "\\?" + "([" + rg_pchar + "/?]|" + rg_pctEncoded + ")*";
var rg_fragment = "\\#" + "([" + rg_pchar + "/?]|" + rg_pctEncoded + ")*";
var rgHttpUrl = new RegExp(
"^"
+ rg_protocol
+ "(" + rg_userinfo + ")?"
+ rg_hostport
+ "(\\/"
+ "(" + rg_path + ")?"
+ "(" + rg_query + ")?"
+ "(" + rg_fragment + ")?"
+ ")?"
+ "$"
);
// export public function
return function (url) {
if (rgHttpUrl.test(url)) {
return true;
} else {
return false;
}
};
})();
RegExp in one line:
var rg = /^(http|https):\/\/(([a-zA-Z0-9$\-_.+!*'(),;:&=]|%[0-9a-fA-F]{2})+#)?(((25[0-5]|2[0-4][0-9]|[0-1][0-9][0-9]|[1-9][0-9]|[0-9])(\.(25[0-5]|2[0-4][0-9]|[0-1][0-9][0-9]|[1-9][0-9]|[0-9])){3})|localhost|([a-zA-Z0-9\-\u00C0-\u017F]+\.)+([a-zA-Z]{2,}))(:[0-9]+)?(\/(([a-zA-Z0-9$\-_.+!*'(),;:#&=]|%[0-9a-fA-F]{2})*(\/([a-zA-Z0-9$\-_.+!*'(),;:#&=]|%[0-9a-fA-F]{2})*)*)?(\?([a-zA-Z0-9$\-_.+!*'(),;:#&=\/?]|%[0-9a-fA-F]{2})*)?(\#([a-zA-Z0-9$\-_.+!*'(),;:#&=\/?]|%[0-9a-fA-F]{2})*)?)?$/;

In a similar situation I got away with this:
someUtils.validateURL = function(url) {
var parser = document.createElement('a');
try {
parser.href = url;
return !!parser.hostname;
} catch (e) {
return false;
}
};
i.e. why invent the wheel if browsers can do it for you? But, of course, this will only work in the browser.
there are various parts of parsed URL exactly how browser would interpret it:
parser.protocol; // => "http:"
parser.hostname; // => "example.com"
parser.port; // => "8080"
parser.pathname; // => "/path/"
parser.search; // => "?search=test"
parser.hash; // => "#hash"
parser.host; // => "example.com:3000"
Using these you can improve your validating function depending on the requirements. The only drawback is that it will accept relative URLs and use current page server's host and port. But you can use it for your advantage, by re-assembling the URL from parts and always passing it in full to your AJAX service.
What validateURL won't accept is invalid URL, e.g. http:\:8883 will return false, but :1234 is valid and is interpreted as http://pagehost.example.com/:1234 i.e. as a relative path.
UPDATE
This approach is no longer working with Chrome and other WebKit browsers. Even when URL is invalid, hostname is filled with some value, e.g. taken from base. It still helps to parse parts of URL, but will not allow to validate one.
Possible better no-own-parser approach is to use var parsedURL = new URL(url) and catch exceptions. See e.g. URL API. Supported by all major browsers and NodeJS, although still marked experimental.

best regex I found from http://angularjs.org/
var urlregex = /^(ftp|http|https):\/\/(\w+:{0,1}\w*#)?(\S+)(:[0-9]+)?(\/|\/([\w#!:.?+=&%#!\-\/]))?$/;

This is what worked for me:
function validateURL(value) {
return /^(https?|ftp):\/\/(((([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(%[\da-f]{2})|[!\$&'\(\)\*\+,;=]|:)*#)?(((\d|[1-9]\d|1\d\d|2[0-4]\d|25[0-5])\.(\d|[1-9]\d|1\d\d|2[0-4]\d|25[0-5])\.(\d|[1-9]\d|1\d\d|2[0-4]\d|25[0-5])\.(\d|[1-9]\d|1\d\d|2[0-4]\d|25[0-5]))|((([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])*([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])))\.)+(([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])*([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])))\.?)(:\d*)?)(\/((([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(%[\da-f]{2})|[!\$&'\(\)\*\+,;=]|:|#)+(\/(([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(%[\da-f]{2})|[!\$&'\(\)\*\+,;=]|:|#)*)*)?)?(\?((([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(%[\da-f]{2})|[!\$&'\(\)\*\+,;=]|:|#)|[\uE000-\uF8FF]|\/|\?)*)?(\#((([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(%[\da-f]{2})|[!\$&'\(\)\*\+,;=]|:|#)|\/|\?)*)?$/i.test(value);
}
from there is is just a matter of calling the function to get a true or false back:
validateURL(urltovalidate);

I know it's quite an old question but since it does not have any accepted answer, I suggest you to use the URI.js framework: https://github.com/medialize/URI.js
You can use it to check for malformed URI using a try/catch block:
function isValidURL(url)
{
try {
(new URI(url));
return true;
}
catch (e) {
// Malformed URI
return false;
}
}
Of course it will consider something like "%#" as a well formed relative URI... So I suggest you read the URI.js API to perform more checks, for example if you want to make sure that the user entered a well formed absolute URL you may do like this:
function isValidURL(url)
{
try {
var uri = new URI(url);
// URI has a scheme and a host
return (!!uri.scheme() && !!uri.host());
}
catch (e) {
// Malformed URI
return false;
}
}

Import in an npm package like
https://www.npmjs.com/package/valid-url
and use it to validate your url.

You can use the URL API that is recently standard. Browser support is sketchy at best, see the link. new URL(str) is guaranteed to throw TypeError for invalid URLs.
As stated above, http://wwww is a valid URL.

The URL API can be used to validate the structure of a URL string.
An error is thrown when trying to serialise an invalid URL string into a URL object. This could be abstracted into a helper function (Typescript snippet below):
function isValidURL(URL: string) : boolean {
try {
new URL(string);
return true;
} catch (err) { return false; }
}
isValidURL('https://www.google.com'); // returns true
isValidURL('localhost:3000'); // returns true
isValidURL('not-a-valid-url'); // returns false
isValidURL('google.com'); // returns false (see footnote)
If you strictly want HTTP / web links to be valid, we can simply add a condition to the return statement:
...
const url = new URL(string);
return url.protocol === 'https:' || url.protocol === 'http:';
...
Granted, this approach comes with a few caveats:
No support for the URL API in Internet Explorer (could be fixed with a polyfill)
Without additional checks, URLs without either a protocol or port are seen as invalid (e.g. google.com is invalid but google.com:3000 is OK). This may be an unintended behaviour for some usecases.

If you're looking for a more reliable regex, check out RegexLib. Here's the page you'd probably be interested in:
http://regexlib.com/Search.aspx?k=url
As for the error messages showing while the person is still typing, change the event from keydown to blur and then it will only check once the person moves to the next element.

var RegExp = (/^HTTP|HTTP|http(s)?:\/\/(www\.)?[A-Za-z0-9]+([\-\.]{1}[A-Za-z0-9]+)*\.[A-Za-z]{2,40}(:[0-9]{1,40})?(\/.*)?$/);

My solution:
function isValidUrl(t)
{
return t.match(/^(http|https|ftp):\/\/(([A-Z0-9][A-Z0-9_-]*)(\.[A-Z0-9][A-Z0-9_-]*)+)(:(\d+))?\/?/i)
}

Demo : http://jsbin.com/uzimeb/1/edit
function checkURL(value) {
var urlregex = new RegExp("^(http|https|ftp)\://([a-zA-Z0-9\.\-]+(\:[a-zA-Z0-9\.&%\$\-]+)*#)*((25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9])\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9]|0)\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9]|0)\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[0-9])|([a-zA-Z0-9\-]+\.)*[a-zA-Z0-9\-]+\.(com|edu|gov|int|mil|net|org|biz|arpa|info|name|pro|aero|coop|museum|[a-zA-Z]{2}))(\:[0-9]+)*(/($|[a-zA-Z0-9\.\,\?\'\\\+&%\$#\=~_\-]+))*$");
if (urlregex.test(value)) {
return (true);
}
return (false);
}

I have found a great resource for comparing different solutions:
https://mathiasbynens.be/demo/url-regex
According to that page, only solution from diegoperini passes all tests. Here is that regex:
_^(?:(?:https?|ftp)://)(?:\S+(?::\S*)?#)?(?:(?!10(?:\.\d{1,3}){3})(?!127(?:\.\d{1,3}){3})(?!169\.254(?:\.\d{1,3}){2})(?!192\.168(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-z\x{00a1}-\x{ffff}0-9]+-?)*[a-z\x{00a1}-\x{ffff}0-9]+)(?:\.(?:[a-z\x{00a1}-\x{ffff}0-9]+-?)*[a-z\x{00a1}-\x{ffff}0-9]+)*(?:\.(?:[a-z\x{00a1}-\x{ffff}]{2,})))(?::\d{2,5})?(?:/[^\s]*)?$_iuS

I checked a lot of url validators in google and no one works for me. For example I'd like to see valid on links like 'aa.com'. I like silly check for dot sign in string.
function isValidUri(str) {
var dotIndex = str.indexOf('.');
return (dotIndex > 0 && dotIndex < str.length - 2);
}
It should not stay on beginning and end of string (for now we don't have top level domain names with one character).

Here's a regular expression which might fit the bill (it's very long):
/^(?:\u0066\u0069\u006C\u0065\u003A\u002F{2}(?:\u002F{2}(?:(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D\u002E\u005F\u007E\u0021\u0024\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u003B\u003D]|\u0025[\u0030-\u0039\u0041-\u0046\u0061-\u0066][\u0030-\u0039\u0041-\u0046\u0061-\u0066])*\u0040)?(?:\u005B(?:(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){6}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035]))|\u003A{2}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){5}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035]))|(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4})?\u003A{2}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){4}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035]))|(?:(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A)?[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4})?\u003A{2}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){3}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035]))|(?:(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){0,2}[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4})?\u003A{2}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){2}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035]))|(?:(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){0,3}[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4})?\u003A{2}[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035]))|(?:(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){0,4}[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4})?\u003A{2}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035]))|(?:(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){0,5}[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4})?\u003A{2}[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){0,6}[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4})?\u003A{2})\u005D|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])|(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039](?:(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D]+)?[\u0041-\u005A\u0061-\u007A\u0030-\u0039])?|(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039](?:(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D]+)?[\u0041-\u005A\u0061-\u007A\u0030-\u0039])?\u002E)+[\u0041-\u005A\u0061-\u007A\u0030-\u0039](?:(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D]+)?[\u0041-\u005A\u0061-\u007A\u0030-\u0039])?))(?:\u003A(?:\u0030-\u0035\u0030-\u0039{0,4}|\u0036\u0030-\u0034\u0030-\u0039{3}|\u0036\u0035\u0030-\u0034\u0030-\u0039{2}|\u0036\u0035\u0035\u0030-\u0032\u0030-\u0039|\u0036\u0035\u0035\u0033\u0030-\u0035))?(?:\u002F(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D\u002E\u005F\u007E\u0021\u0024\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u003B\u003D\u003A\u0040]|\u0025[\u0030-\u0039\u0041-\u0046\u0061-\u0066][\u0030-\u0039\u0041-\u0046\u0061-\u0066])*)*|\u002F(?:(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D\u002E\u005F\u007E\u0021\u0024\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u003B\u003D\u003A\u0040]|\u0025[\u0030-\u0039\u0041-\u0046\u0061-\u0066][\u0030-\u0039\u0041-\u0046\u0061-\u0066])+(?:\u002F(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D\u002E\u005F\u007E\u0021\u0024\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u003B\u003D\u003A\u0040]|\u0025[\u0030-\u0039\u0041-\u0046\u0061-\u0066][\u0030-\u0039\u0041-\u0046\u0061-\u0066])*)*)?|(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D\u002E\u005F\u007E\u0021\u0024\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u003B\u003D\u003A\u0040]|\u0025[\u0030-\u0039\u0041-\u0046\u0061-\u0066][\u0030-\u0039\u0041-\u0046\u0061-\u0066])+(?:\u002F(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D\u002E\u005F\u007E\u0021\u0024\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u003B\u003D\u003A\u0040]|\u0025[\u0030-\u0039\u0041-\u0046\u0061-\u0066][\u0030-\u0039\u0041-\u0046\u0061-\u0066])*)*)|[\u0041-\u005A\u0061-\u007A][\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002B\u002D\u002E]*\u003A(?:\u002F{2}(?:(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D\u002E\u005F\u007E\u0021\u0024\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u003B\u003D]|\u0025[\u0030-\u0039\u0041-\u0046\u0061-\u0066][\u0030-\u0039\u0041-\u0046\u0061-\u0066])*\u0040)?(?:\u005B(?:(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){6}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035]))|\u003A{2}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){5}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035]))|(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4})?\u003A{2}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){4}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035]))|(?:(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A)?[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4})?\u003A{2}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){3}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035]))|(?:(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){0,2}[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4})?\u003A{2}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){2}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035]))|(?:(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){0,3}[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4})?\u003A{2}[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035]))|(?:(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){0,4}[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4})?\u003A{2}(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035]))|(?:(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){0,5}[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4})?\u003A{2}[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}|(?:(?:[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4}\u003A){0,6}[\u0030-\u0039\u0041-\u0046\u0061-\u0066]{1,4})?\u003A{2})\u005D|(?:(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])\u002E){3}(?:[\u0030-\u0039]|[\u0031-\u0039][\u0030-\u0039]|\u0031[\u0030-\u0039]{2}|\u0032[\u0030-\u0034][\u0030-\u0039]|\u0032\u0035[\u0030-\u0035])|(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039](?:(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D]+)?[\u0041-\u005A\u0061-\u007A\u0030-\u0039])?|(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039](?:(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D]+)?[\u0041-\u005A\u0061-\u007A\u0030-\u0039])?\u002E)+[\u0041-\u005A\u0061-\u007A\u0030-\u0039](?:(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D]+)?[\u0041-\u005A\u0061-\u007A\u0030-\u0039])?))(?:\u003A(?:\u0030-\u0035\u0030-\u0039{0,4}|\u0036\u0030-\u0034\u0030-\u0039{3}|\u0036\u0035\u0030-\u0034\u0030-\u0039{2}|\u0036\u0035\u0035\u0030-\u0032\u0030-\u0039|\u0036\u0035\u0035\u0033\u0030-\u0035))?(?:\u002F(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D\u002E\u005F\u007E\u0021\u0024\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u003B\u003D\u003A\u0040]|\u0025[\u0030-\u0039\u0041-\u0046\u0061-\u0066][\u0030-\u0039\u0041-\u0046\u0061-\u0066])*)*|\u002F(?:(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D\u002E\u005F\u007E\u0021\u0024\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u003B\u003D\u003A\u0040]|\u0025[\u0030-\u0039\u0041-\u0046\u0061-\u0066][\u0030-\u0039\u0041-\u0046\u0061-\u0066])+(?:\u002F(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D\u002E\u005F\u007E\u0021\u0024\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u003B\u003D\u003A\u0040]|\u0025[\u0030-\u0039\u0041-\u0046\u0061-\u0066][\u0030-\u0039\u0041-\u0046\u0061-\u0066])*)*)?|(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D\u002E\u005F\u007E\u0021\u0024\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u003B\u003D\u003A\u0040]|\u0025[\u0030-\u0039\u0041-\u0046\u0061-\u0066][\u0030-\u0039\u0041-\u0046\u0061-\u0066])+(?:\u002F(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D\u002E\u005F\u007E\u0021\u0024\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u003B\u003D\u003A\u0040]|\u0025[\u0030-\u0039\u0041-\u0046\u0061-\u0066][\u0030-\u0039\u0041-\u0046\u0061-\u0066])*)*)(?:\u003F(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D\u002E\u005F\u007E\u0021\u0024\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u003B\u003D\u003A\u0040\u002F\u003F]|\u0025[\u0030-\u0039\u0041-\u0046\u0061-\u0066][\u0030-\u0039\u0041-\u0046\u0061-\u0066])*)?(?:\u0023(?:[\u0041-\u005A\u0061-\u007A\u0030-\u0039\u002D\u002E\u005F\u007E\u0021\u0024\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u003B\u003D\u003A\u0040\u002F\u003F]|\u0025[\u0030-\u0039\u0041-\u0046\u0061-\u0066][\u0030-\u0039\u0041-\u0046\u0061-\u0066])*)?)$/
There are some caveats to its usage, namely it does not validate URIs which contain additional information after the user name (e.g. "username:password"). Also, only IPv6 addresses can be contained within the IP literal syntax and the "IPvFuture" syntax is currently ignored and will not validate against this regular expression. Port numbers are also constrained to be between 0 and 65,535. Also, only the file scheme can use triple slashes (e.g. "file:///etc/sysconfig") and can ignore both the query and fragment parts of a URI. Finally, it is geared towards regular URIs and not IRIs, hence the extensive focus on the ASCII character set.
This regular expression could be expanded upon, but it's already complex and long enough as it is. I also cannot guarantee it's going to be "100% accurate" or "bug free", but it should correctly validate URIs for all schemes.
You will need to do additional verification for any scheme-specific requirements or do URI normalization as this regular expression will validate a very broad range of URIs.

Try edit your isValidURL function as follows:
function isValidURL(url) {
var encodedURL = encodeURIComponent(url);
var isValid = false;
$.ajax({
url: "http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20html%20where%20url%3D%22" + encodedURL + "%22&format=json",
type: "get",
async: false,
dataType: "json",
success: function(data) {
isValid = data.query.results != null;
},
error: function(){
isValid = false;
}
});
return isValid;
}
This should do the trick.