How to Check if User entered text contains http:// in Javascript

Question

I have a setup like, My website ask the user for entering a URL. Sometimes user enters like http://google.com/ and other times google.com , but my application supports URL with http:// or https:// ,
I tried this:

var a = document.getElementById('tinput').value;
if (a.indexOf(escape('http://')) < 0 && a.indexOf(escape('https://')) < 0){
b = 'http://' + a;
document.getElementById('tinput').value = b;
}
document.getElementById("urlfrm").submit();

But this dint work. It always adds http:// to all the URL even if they contain the same. What to do?

Answer 1

Try

var a = document.getElementById('tinput').value;
if (a.indexOf('http://') == -1 && a.indexOf('https://') == -1){
b = 'http://' + a;
document.getElementById('tinput').value = b;
document.getElementById("urlfrm").submit();
} else {
document.getElementById("urlfrm").submit();
}

Answer 2

Try this:

var field = document.getElementById('tinput');
if (!/^https?:\/\//.test(field.value)) field.value = 'http://'+field.value;

A couple of points to note:

• your current check allows for http(s):// to be anywhere in the string - you should check for it at the start only

• in the interests of code readability, and because the only value under zero that indexOf() can return is -1, it's better to check for that explicitly, rather than < 0

• you're creating a global variable ( b ) for no reason

• don't escape - as xdevel said in his comment, this will mean you check for an encoded version of the string, not the string itself

Answer 3

You can do this simply with regular expressions, well worth learning about them.

if ( a.match("^https?://") ) {
    alert("a is a url");
}