Develop Reference

How to implement a function that will return when an intense string is passed in, and false otherwise?

Strings are intense if they end in three or more more ! marks. However, having ! marks anywhere but the end makes for a non-intense string.
The issue I'm having is when there is an ! in the middle of a string. The result should be false but it's still resulting as true.
My code:
function intenseString (str) {
if (str.slice(-3) !== "!!!") {
return false;
}
else if(str.slice(str.indexOf("!"))){
return false;
}
else if(str.slice(-3) === "!!!"){
return true
}
}

Use indexOf instead of slicing the string:
const strings = ['abc!!!', 'abc!!de', 'abc!']
const intenseString = (str, chars) => str.indexOf(chars) >= 0
console.log(strings.map(x => intenseString(x, '!!!')))

Here's your code, with some formatting tweaks for readability:
function intenseString(str) {
if (str.slice(-3) !== '!!!') {
return false;
}
if (str.slice(str.indexOf('!'))) {
return false;
}
if (str.slice(-3) === '!!!') {
return true;
}
}
Can you give some example inputs that return true? I don't think this will ever return true because the second if statement says "return false if there are any !'s in the string, which is implied by passing the first if.
I believe you meant to add + 1: if (str.slice(str.indexOf('!') + 1)) return false which says "return false if there are any !'s that are not the last character in the string", which still won't work: The first if statement will return false if the string doesn't end with !!! meaning that the smallest string that would get to the second if statement is !!! and there will always be characters after the first !.
Another potential attempt would be to only check the string before the last three characters if (str.slice(0, -3).slice(str.indexOf('!') + 1)) return false, which almost works except for strings containing more than 4 ! at the very end... (such as !!!!!).
I don't see a simple way (without regex to check that the remaining characters are only !) to make the second if statement work without looping over the string.
Note that your final if is unnecessary. Your first two are checking for failure and if they pass through them, it must be an intenseString. Also the string must end in !!! if it got past the first if.
Here's a potential solution which goes through every character in the string, except for the last 4, and returns false if there is ever an ! followed by something that is not an !.
function intenseString(str) {
if (!str.endsWith('!!!')) {
return false;
}
for (let i = 0; i < str.length - 4; i++) {
if (str.charAt(i) === '!' && str.charAt(i + 1) !== ('!')) {
return false;
}
}
return true;
}

Try one of these ways:
function intenseString(str) { return str.slice(-3) === '!!!'; }
function intenseString(str) { return str.endsWith('!!!'); }
function intenseString(str) { return /!{3}$/.test(str); }

Why this regular expression return false?

i have poor eng, Sorry for that.
i'll do my best for my situation.
i've tried to make SignUpForm using regular expression
The issue is that when i handle if statement using the regular expression
result is true at first, but after that, become false. i guess
below is my code(javascript)
$(document).ready(function () {
var idCheck = /^[a-z]+[a-z0-9]{5,19}$/g; // more than 6 words
var pwCheck = /^(?=.*[A-Za-z])(?=.*\d)[A-Za-z\d]{8,}$/; // more than 8 words including at least one number
var emCheck = /^([\w-]+(?:\.[\w-]+)*)#((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$/; // valid email check
var signupConfirm = $('#signupConfirm'),
id = $('#id'),
pw = $('#pw'),
repw = $('#repw'),
email =$('#email');
signupConfirm.click(function () {
if(id.val() === '' || pw.val() === '' || email.val() === ''){
$('#signupForm').html('Fill the all blanks');
return false;
} else {
if (idCheck.test(id.val()) !== true) {
$('#signupForm').html('ID has to be more than 6 words');
id.focus();
return false;
} else if (pwCheck.test(pw.val()) !== true) {
$('#signupForm').html('The passwords has to be more than 8 words including at least one number');
pw.focus();
return false;
} else if (repw !== pw) {
$('#signupForm').html('The passwords are not the same.');
pw.empty();
repw.empty();
pw.focus();
return false;
}
if (emCheck.test(email.val()) !== true) {
$('#signupForm').html('Fill a valid email');
email.focus();
return false;
}
}
})
});
after id fill with 6 words in id input, focus has been moved to the password input because the condition is met.
but after i click register button again, focus move back ID input even though ID input fill with 6 words
i've already change regular expression several times. but still like this.
are there Any tips i can solve this issue?
I hope someone could help me.
Thank you. Have a great day

Do not use the global flag on your regexes. Your code should be:
var idCheck = /^[a-z]+[a-z0-9]{5,19}$/;
When you match with the /g flag, your regex will save the state between calls, hence all subsequent matches will also include the previous inputs.

use
var idCheck = /^[a-z]+[a-z0-9]{5,19}$/
removing the g flag
and modify the line
else if (repw.val() !== pw.val()) {

Validating phone numbers. Null is not an object

I'm doing a challenge on Freecodecamp. I'm having a problem that seems to make no sense to me.
function telephoneCheck(str) {
// if string contains a letter then return false //
var exc = /[a-z\?/]/;
// check str to see if it has anything from the //
// regex and then make it into a string. //
var excJoin = str.match(exc).join('');
// if theres something in the //
// variable(something was found with regex) //
// then return false //
if(excJoin.length > 0) {
return false;
}
// else return true //
if(excJoin === null){return true;}
}
telephoneCheck("2(757)622-7382");
Returning false is fine, however when I just want to say else {return true;} it tells me null is not an object. What's the problem?
http://freecodecamp.com/challenges/validate-us-telephone-numbers

String.prototype.match (in your code: str.match(exc)) returns null if it didn't match the regex, so then the code is equivalent to null.join(''), which is an error.
Instead, check if it's null first:
var excResult = str.match(exc);
if (excResult === null) {
// didn't match, do something
} else {
// did match, do something else
}

You must test for nullity before using the object

str.match(exc) returns null if there are no founds for the given pattern.
So your code should do this:
function telephoneCheck(str) {
// if string contains a letter then return false
var exc = /[a-z\?/]/;
//The match() method retrieves the matches when matching a string against a regular expression.
var excResult= str.match(exc);
//return false if there is a found
if(excResult != null) {
return false;
}
else{
//there is no found cause excResult == null
return true;
}
telephoneCheck("2(757)622-7382");

Regex for http:// but not https://

I need to flag a textarea that contains a URL starting with http://, but not with https://. I thought this should work, but I'm getting the alert even when all URLs are https.
$('#template_form').submit(function() {
alert("this is the text: " + $("#template_data").val() );
val = $("#template_data").val();
if (val.search(/^http:\/\//)){
alert("there's a URL in there...");
return false;
}
return true;
});
<textarea id="template_data">This is a test of the new URL validation. Let's add a link to https://www.test.com</textarea>
This should only present the second alert if the URL were http://www.test.com, but it's throwing it even as is, with https://. What am I doing wrong?

From the documentation for search():
A String method that tests for a match in a string. It returns the index of the match, or -1 if the search fails.
-1 will make the if statement evaluate to true (if (-1) {alert("true");}. So either switch to match() or test(), or check for if (val.search(...) > -1)
Also the ^ is wrong in your regex, it would only match from the start of the string.
$('#template_form').submit(function() {
alert("this is the text: " + $("#template_data").val());
val = $("#template_data").val();
if (val.match(/http:\/\//)) {
alert("there's a URL in there...");
return false;
}
return true;
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<form id="template_form">
<textarea id="template_data">This is a test of the new URL validation. Let's add a link to https://www.test.com</textarea>
<input type="submit" value="submit">
</form>

String.search() is not boolean:
Return value
The index of the first match between the regular expression and the given string; if not found, -1.
Further in that same piece of documentation:
When you want to know whether a pattern is found and also its index in
a string use search() (if you only want to know it exists, use the
similar test() method, which returns a boolean)

$('#template_form').submit(function() {
if ($("#template_data").val().indexOf("http:\/\/") > -1) {
return false;
}
return true;
});
Here is another way.

Javascript Replace - Regular Expression

I need to replace a code example: OD3 - The first must always be alpha character, 2nd alphanumeric and the last must always be numeric. What's the regular expression to check and replace the first and regulate the rest to enter correctly? A user could enter in the number 0 instead of the letter O, so I want to correct it immediately...
this is what I have so far: onkeyup="this.value=this.value.replace(/[^a-zA-z]/g,'')

First, I'd suggest just indicating the error to a user instead of replacing the values. Something like
oninput="if (! /^[a-z][a-z0-9]\d$/i.test(this.value) ) displayMessage('incorrect code');"
If you definitely have to replace the value on the fly, you could do somthing like that:
oninput='validateValue()';
...
function validateValue() {
var val = this.value;
if (! /[a-z]/i.test(val[0]) this.value = '';
else if (! /[a-z0-9]/i.test(val[1]) this.value = val.slice(0,1);
else if (! /\d/.test(val[2]) this.value = val.slice(0,2);
}

Better have like this.
onkeyup="testRegex(this.value)";
It is not .replace() it is .test()
function testRegex(value) {
if(value.test(/[^a-zA-z]/g)) {
alert("Please enter correct value");
return false;
}
}