return a substring using indexOf as a parameter within a function

Question

I'm supposed to create a functions to test a URL for validity then functions to look for and return parts of the URL string based on location of certain characters (position would be unknown). FYI, I'm very new to programming but have been searching and trying many answers. My latest attempt uses below format (found in an answer) but still can not get anything but an empty string to display when I call the function.

When I run this in Chrome, and enter "http://www.niagaracollege.ca" or "http://lego.ca" even though I am entering a valid URL, I get a return of false.

function validURL(userInput)
{
    input = new String(userInput);

    if (input.indexOf("://") != -1 && input.lastIndexOf(".") != -1)
        return true;

    else
        return false;
  }

 function findProtocol(userInput)
{
    input = new String(userInput);
    var result = input.substring(0, input.indexOf("://"));
    return result;
}

function findServer(userInput)
{   
    input = new String(userInput);

    var result = input.substring(input.indexOf("://") + 1 ,input.lastIndexOf("."));

    return result;
}

function findDomain(userInput)
{
    input = new String(userInput);

    var result = input.substring(input.lastIndexOf(".") + 1);

    return result;
}

function btnReadURL_onclick()
{
    var userInput = document.getElementById("txtURL").value;

    var outputBox = document.getElementById("txtOutput");

    var URL = validURL(userInput);

    if (URL = true)
    {
       var Part1 = findProtocol(userInput);
       var Part2 = findServer(userInput);
       var Part3 = findDomain(userInput);

       outputBox.value = "Protocol: " + Part1 + "\nServer: " + Part2 + 
    "\nDomain: " + Part3;
    }   

    else (URL == true)
       outputBox.value = "Invalid URL"; 
 }

@gurvinder372 The name of the OP's function kind of implies that. — Tomalak, Mar 21 '16 at 06:56
@Tomalak true, but it doesn't specify - `from what` part of it. — gurvinder372, Mar 21 '16 at 06:57
Your function works. It is not optimal, but it works. What do you test it with? — Tomalak, Mar 21 '16 at 06:57
@gurvinder - we are to check validity of a Url - this is one of the functions I have to create out of 4. — Tyzer, Mar 21 '16 at 07:02
So, URL is passed to this function as parameter? In that case your method should work. Can you elaborate on what is not working? — gurvinder372, Mar 21 '16 at 07:04
@Tomalak - I have a html file with a button and js file with 4 functions and the event handler function. I checked it by opening the html in chrome. — Tyzer, Mar 21 '16 at 07:05
It should provide that part of the string when I call it but I get nothing. Should I show the entire code? — Tyzer, Mar 21 '16 at 07:07
@Tyzer yes show the entire code, I think something is missed out — gurvinder372, Mar 21 '16 at 07:07
Please [edit] your question, and show the relevant JavaScript there, where it can be read, not in the comments where it's incredibly difficult to read. — David Thomas, Mar 21 '16 at 07:14
full code has been added to the question. Thanks @DavidThomas. — Tyzer, Mar 21 '16 at 07:24

score 1 · Answer 1 · answered Mar 21 '16 at 07:06

1

Use a debugger to find out what you are getting in the userInput. The code is fine. It should work. See sample code below.

test = function() {
    var test = "http://Test 2"
    alert(test.substring(0, test.indexOf("://")))
}

answered Mar 21 '16 at 07:06

user883986

21
1

gurvinder372 · Accepted Answer · 2016-03-21T11:20:51.150

0

You need to pass the value to the findProtocol method rather than DOM element

Replace

var userInput = document.getElementById("txtURL");

by

var userInput = document.getElementById("txtURL").value;

and replace

if (URL = true)

with

if( URL == true )

edited Mar 21 '16 at 11:20

answered Mar 21 '16 at 07:33

gurvinder372

66,980
10
72
94

that solved the empty string problem. Does anyone know why I'm not getting any false returns on the validURL function? – Tyzer Mar 21 '16 at 11:16
I made second change. Now all my URL tests come back invalid even when they should be valid. What else is wrong? – Tyzer Mar 21 '16 at 11:25
http://www.lego.ca, http://ww.niagaracollege.ca. It shouldn't matter if the URL is an actual site, as the validity fuction is just checking if "://" AND "." both exist for it to be true. In both examples, I get the result of false. – Tyzer Mar 21 '16 at 11:43
@Tyzer because neither of these two examples has `://` in it – gurvinder372 Mar 21 '16 at 11:45
Sorry - I guess they needed to be in quotes - it automatically made them links but I didn't realize that. I entered "http://lego.ca" and then "http://niagaracollege.ca" – Tyzer Mar 21 '16 at 11:46
why will the comment area here not show the "http://" before the web address like I'm typing? – Tyzer Mar 21 '16 at 11:48
@Tyzer can you update your question to share what input did you tried with **updated code**? – gurvinder372 Mar 21 '16 at 11:49

return a substring using indexOf as a parameter within a function

2 Answers2