function within a loop within a function? - function

Question

I'm coding an email verification form in 3 parts.
Part 1 - check a single character against a list of allowed characters and return true/false.
Part 2 - check a string of characters as the part before or after the '#' using a loop calling the previous function to each successive character.
Part 3 - check a complete email that it includes only one '#', the substring before and after the '#' both satisfy part 2 and the substring following the '#' has only one full stop.
I've got part 1 down but my loop for part 2 is incorrect and returning true for all input values other than a blank form. here is the code -
function isValidEmailPart(part)
{ var emailPartInput = document.getElementById("isValidPartArg").value;
var emailPartLength = alert(emailPartInput.length);
{
if (emailPartInput.length == "")
{
return (false)
}
else
{
NUMBER_OF_CHARACTERS = alert((emailPartInput.length) - 1);
var i = 0;
{for(var i=0; i<NUMBER_OF_CHARACTERS; i++)
{
function isValidEmailChar()
{ var validChars = 'a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z,0,1,2,3,4,5,6,7,8,9,_,-,.,';
var emailPartInput = document.getElementById("isValidPartArg").value;
var charInput = emailPartInput.charAt(i);
var inputVar = validChars.indexOf(charInput);
if (inputVar < 0)
{
return (false)
}
}
}
return (true);
}
}
}
}
I know it must be something simple, there are no errors returning I have no idea what I'm doing wrong.

Answer 1

Please, consider the following things very carefully:
Define functions separately: you can call a function from another function BUT don't define a function inside a function
Make sure that your code is ok, pay attention to your code syntax: I found additional { for example. Usually your code editor highlights code syntax errors.
Pay attention to your code's indent: having a good indent helps you have a clearer view of your code and helps you find your potential code mistakes.
Review the different types of variables: in javascript, the variables can have different types: boolean, integer, float, string, etc. You can only compare variables of a same types (Do not mix carrots and potatoes!) and so, you cannot compare emailPartInput with an empty string "" for example.
Before reading the code bellow, you should try to search what was wrong it your code, and what has to be modified to make it work.
Check very carefully the comments I wrote in the code that follows (I took a lot of time to write them!)
The javascript functions:
// This functions verifies if a char 'my_char' is valid
function isValidEmailChar(my_char)
{
// 'my_char' is a i-th character of 'emailPartInput'
var output = false;
// 'validChars' is the array containing all the valid characters
var validChars = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',
'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z',
'0','1','2','3','4','5','6','7','8','9','_','-','.'];
// We want to check if 'my_char' is in the array 'validChar'
// So, for each character in the array 'validChar', we check that there's at least
// 1 character in it which is equal to 'my_char'
for(var i=0; i<validChars.length; i++)
{
// 'output' is the result that the function 'isValidEmailChar' will return
// It is initially set to "false"
// The line below means: we store in 'output'
// the result of " output OR ['my_char' EQUALS the i-th character in the array 'validChars'] ".
// Which means that, in the end, 'output' will be "true" if there's at least one i-th character
// in the array 'validChars' where 'my_char' EQUALS the i-th character in the array 'validChars'.
output = (output || (my_char == validChars[i]));
}
// We return the output
// Note: It is better to define 1 'return' and not several
return output;
}
// This function verifies if a part of Email is valid
function isValidEmailPart(emailPartInput)
{
// 'emailPartInput' is the part of email
// 'output' is your function's result to be returned
var output = false;
alert("INPUT = "+emailPartInput);
var nb_of_characters = emailPartInput.length;
alert("number of characters = "+nb_of_characters);
if (nb_of_characters != 0)
{
output = true;
var i = 0;
while(output && i<nb_of_characters)
{
// 'is_character_valid' is a boolean value which is set to:
// - true: if the i-th character of 'emailPartInput' is valid
// - false: if not valid
var is_character_valid = isValidEmailChar(emailPartInput.charAt(i));
// The line below means that we store in the variable 'ouput' the result of
// 'output' AND 'is_character_valid', which means that:
// if there's at least one 'is_character_valid' set to false
// (= one i-th character of 'emailPartInput' is not valid)
// 'output' will then be equals to false
output = output && is_character_valid;
i++;
// We remark that if 'output' is false, we quit the 'while' loop
// because finding one invalid character means that 'emailPartInput' is invalid
// so, we do not need to check the other characters of 'emailPartInput'
}
}
else
{
alert("No emailPartInput has been input");
}
// We return the output
return output;
}
Here's a working example where you can test your functions:
<HTML>
<HEAD>
<SCRIPT language="javascript">
// This functions verifies if a char 'my_char' is valid
function isValidEmailChar(my_char)
{
// 'my_char' is a i-th character of 'emailPartInput'
var output = false;
// 'validChars' is the array containing all the valid characters
var validChars = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',
'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z',
'0','1','2','3','4','5','6','7','8','9','_','-','.'];
// We want to check if 'my_char' is in the array 'validChar'
// So, for each character in the array 'validChar', we check that there's at least
// 1 character in it which is equal to 'my_char'
for(var i=0; i<validChars.length; i++)
{
// 'output' is the result that the function 'isValidEmailChar' will return
// It is initially set to "false"
// The line below means: we store in 'output'
// the result of " output OR ['my_char' EQUALS the i-th character in the array 'validChars'] ".
// Which means that, in the end, 'output' will be "true" if there's at least one i-th character
// in the array 'validChars' where 'my_char' EQUALS the i-th character in the array 'validChars'.
output = (output || (my_char == validChars[i]));
}
// We return the output
// Note: It is better to define 1 'return' and not several
return output;
}
// This function verifies if a part of Email is valid
function isValidEmailPart(emailPartInput)
{
// 'emailPartInput' is the part of email
// 'output' is your function's result to be returned
var output = false;
alert("INPUT = "+emailPartInput);
var nb_of_characters = emailPartInput.length;
alert("number of characters = "+nb_of_characters);
if (nb_of_characters != 0)
{
output = true;
var i = 0;
while(output && i<nb_of_characters)
{
// 'is_character_valid' is a boolean value which is set to:
// - true: if the i-th character of 'emailPartInput' is valid
// - false: if not valid
var is_character_valid = isValidEmailChar(emailPartInput.charAt(i));
// The line below means that we store in the variable 'ouput' the result of
// 'output' AND 'is_character_valid', which means that:
// if there's at least one 'is_character_valid' set to false
// (= one i-th character of 'emailPartInput' is not valid)
// 'output' will then be equals to false
output = output && is_character_valid;
i++;
// We remark that if 'output' is false, we quit the 'while' loop
// because finding one invalid character means that 'emailPartInput' is invalid
// so, we do not need to check the other characters of 'emailPartInput'
}
}
else
{
alert("No emailPartInput has been input");
}
// We return the output
return output;
}
function test() {
var my_input = document.getElementById("my_input").value;
var result = isValidEmailPart(my_input);
if(result)
alert("The part of email is valid");
else
alert("The part of email is NOT valid");
}
</SCRIPT>
</HEAD>
<BODY>
Enter you Email part here:
<INPUT type="text" id="my_input" value="" />
<button onclick="javascript:test();">Check the Email part!</button>
</BODY>
</HTML>
NB: The most important is to make sure that you understand what you wrote in your code and what was wrong.
I think you know that just copying a working won't be a benefit for you.
If you read my code, I hope you spent your time to understand it and to read the comments carefully (I took a lot of time to write them! :S)
You can check free online tutorials to learn javascript too! :)
Hope this helps. If you have any questions, do not hesitate to ask, I'll be glad to help.