checkUrl.js

function isUrl(url) {
    var re = /^(http\:\/\/|https\:\/\/)?([a-z0-9][a-z0-9\-]*\.)+[a-z0-9][a-z0-9\-]*[a-z0-9]$/i;
    return re.test(url);
}


console.log(isUrl('12domain.ru')); // true
console.log(isUrl('www.domain.com')); // true
console.log(isUrl('http://domain.com')); // true
console.log(isUrl('https://domain.com')); // true


console.log(isUrl('-12domain.ru')); // false
console.log(isUrl('www.domain.c')); // false
console.log(isUrl('http://domain.com-')); // false
console.log(isUrl('https:/domain.com')); // false