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Compare string with GM_GetValue not working as excepted

I am trying to compare value of TestScript with string "Investisseur" But this seems not working and I don't go into the if statement.
console.log(GM_getValue(TestScript));
if(GM_getValue(TestScript) == "Investisseur")
{
//Should be there
}
console.log(GM_getValue(TestScript)); returns :
So the if condition would return true and not false .. What Am I doing Wrong ?
EDIT
It seems like the check before reset my #GM_getValue:
if(GM_getValue(TestScript) == "Investisseur" || GM_getValue(TestScript) == null || GM_getValue(TestScript) == undefined ){
GM_setValue(TimeoutMain, 1000)
}else if(GM_getValue(TestScript) == "Emetteur"){
GM_setValue(TimeoutMain, 10000)
}
Any Idea why ? When I try to Console.log after this it display nothing .. Why is the value deleted ?
Maybe more understandable with a screen there :

TestScript might have extra spaces.
trim() removes leading and trailing whitespace.
Try replacing:
GM_getValue(TestScript)
with:
if (GM_getValue(TestScript).trim() == "Investisseur")

How do I check if a variable is null, so that I can change it later on?

A group of me and two other people are working to make a Jeopardy game (themed around United States History questions) all in JavaScript. For our final Jeopardy screen, the two teams will each bet a certain amount of money. To prevent a team from typing in random letters for a bet (i.e typing in "hasdfhgasf" instead of an actual amount), we're trying to write an 'onEvent' command that checks to see if a bet is null. If that bet is null, then the code should come up with a message on the screen that tells them to check their bets again.
We tried using statements like, if "null" or if " " but neither of these statements works. We've worked with using getNumber and getText commands, along with just regular variable comparisons with or booleans. So far, we haven't had any luck with these methods.
Here's the group of code we're having issues with:
onEvent("finalJeopardyBetSubmit", "click", function() {
team1Bet = getNumber("team1BetInput");
team2Bet = getNumber("team2BetInput");
console.log(team1Bet);
console.log(team2Bet);
if (getText("team1BetInput") == "" || getText("team2BetInput") == "") {
console.log("Check bet!");
finalJeopardyError();
} else if ((getText("team1BetInput") != 0 || getText("team2BetInput") != 0)) {
console.log("Check bet!");
finalJeopardyError();
} else if ((getNumber("team1BetInput") < 0 || getNumber("team2BetInput") < 0)) {
console.log("Check bet!");
finalJeopardyError();
} else if ((getNumber("team1BetInput") > team1Money || getNumber("team2BetInput") > team2Money)) {
console.log("Check bet!");
finalJeopardyError();
} else {
console.log("Done");
}
});
You can also check out the whole program on Code.org if you'd like to get a better look.
We expect that with the console.log commands, it should say "check bet" if the bets return as null. Instead, the code has ended up fine, and not displaying our error message, even if we type in nothing or just random letters.

a null variable will evaluate to false. Try:
if(variable){
// variable not null
}else{
// variable null
}

Convert the value to a Number first using Number(value) and then check for falsy values using the logical not ! operator. If they enter alphabetic characters, then calling Number('abc') results in NaN.
If a value can be converted to true, the value is so-called truthy. If
a value can be converted to false, the value is so-called falsy.
Examples of expressions that can be converted to false are:
null; NaN; 0; empty string ("" or '' or ``); undefined.
The ! will change any of the falsy values above to true, so you can check for all of them with just the first if statement below.
onEvent("finalJeopardyBetSubmit", "click", function() {
// Convert these values to numbers first
var team1Bet = Number(getNumber("team1BetInput"));
var team2Bet = Number(getNumber("team2BetInput"));
if (!team1Bet || !team2Bet) {
// Handle invalid number error
}
else if (team1Bet < 0 || team2Bet < 0) {
// Handle invalid range error
}
else if (team1Bet > team1Money || team2Bet > team2Money) {
// Handle insufficient funds error
}
else {
// Finish game
}
})
You can read more about the logical operators here.

How to successfully break out of function in javascript?

So I have a function that checks if the last character in a string is an arithmetic operator(+,-,*,/), and if it is it should immediately return from the function. If not, the subtract sign should be appended to the string. However, only the second case seems to be occurring and I can't figure out why. If anyone could provide some insight I would be very appreciative.
$("#subtract").click(function () {
var original=$("#display").text();
var sliced=original.slice(0,original.length - 1);
var signs=["+","-","*","/"];
var charpos=sliced.charAt(sliced.length -1);
if ((charpos === signs[0]) || (charpos === signs[1]) || (charpos === signs[2]) || (charpos === signs[3])) {
return;
}
else {
var newdisplay=sliced + "-";
$("#display").text(newdisplay);
}
});

You're slicing the input which is removing the last character, then using charAt and getting the second to last character.
var original=$("#display").text(); // "foobar"
var sliced=original.slice(0,original.length - 1); // "fooba"
var charpos=sliced.charAt(sliced.length -1); // "a" -- we lost the "r"
You only need to call charAt and work with the last character (or, if you prefer slice, it's able to accept a negative number and backtrack the string).
Secondly, since signs is an array, you can use indexOf over checking each element. e.g.
var original = $('#display').text();
var signs = ["+","-","*","/"];
var lastChar = original.slice(-1); // OR original.charAt(original.length - 1);
// Check for the lastChar in the signs array
if (signs.indexOf(lastChar) != -1){ // -1 == not found
return; // short exit
}

var original=$("#display").text();
var sliced=original.slice(0,original.length - 1);
the second line gets rid of the last character in your string. so you're not even able to check what that was. just get rid of it and change the first line to
var sliced=$("#display").text();
and everything should work fine

Instead of
if ((charpos === signs[0]) || (charpos === signs[1]) || (charpos === signs[2]) || (charpos === signs[3])) {
return;
}
try
if ($.inArray(charpos, signs) > -1) {
return;
}
First of all, never enumerate items from an array in such a fashion - it's easy to miss items that way. Secondly, exact instance comparison (===) won't fire, unless you compared exact same strings.
Besides, consider revising how you extract the last character.

Integer validation not working as expected

Thanks to some of the answers on this site, I built a function to validate an integer inside a prompt in javascript. I found out how to use isNaN and the result of % in order to meet my needs, but there must be something wrong, because is still not working: This function for validation needs to accept only integers, and as extra bonus, it will also accept a special keyword used for a different purpose later on in the program.
So, previously I had defined:
var value = prompt("Type an integer");
So after that, I made a call for the validation function, and that included three conditions: The validation warning would jump if:
1) The string is not a number
2) The string % 1 is not 0 (means is not an integer)
3) The string is not the special keyword ("extra") which is also valid as input.
The function needs to loop and keep showing the prompt until a valid data is written.
while (isNaN(value) == true && value % 1 != 0 && value != "extra") {
alert("Please, type an integer");
var value = prompt("Type an integer");
}
What am I doing wrong? Thank you so much for any ideas. I know the integer validation has been asked many times here, and here I got a few ideas, but I might be missing something...

You might be complicating things too much... A quick regular expression will do the trick.
while (!/^(\d+|extra)$/i.test(value)) {
...
}

You typed only one equal at
isNaN(value) = true

jsFiddle example
var int = 10;
var str = "10";
var isInt = function(value) {
return (str === 'extra' || !isNaN(parseInt(value, 16)) || /^\d+$/.test(value));
};
var isIntStrict = function(value) {
return (isInt(value) && typeof value !== 'string');
}
console.log('false', isInt('kirk'));
console.log('true', isInt(int));
console.log('true', isInt(str));
console.log('true', 'strict - int', isIntStrict(int));
console.log('false','strict - string', isIntStrict(str));
console.log('false','strict - string', isIntStrict('0x04'));
console.log('true','strict - string', isIntStrict(0x04));

I assume that for your purposes #elclanrs' answer is all you need here, and is the simplest and most straightforward, but just for completeness and dubious laughs, I'm pretty sure that the following would also do what you're looking for:
function isAnIntOrExtra(v) {
if (parseInt(+v) === +v && v !== '') {
return parseInt(+v);
}
else if (v === 'extra') {
return v;
}
else {
return false;
}
}
Fiddle here
These should all pass and return an integer in decimal notation:
'387' returns 387
'-4' returns -4
'0' returns 0
'2.4e3' returns 2400
'0xf4' returns 244
while these should all fail:
'4.5' returns false
'2.4e-3' returns false
'0xgc' returns false
'' returns false
'seven' returns false
And the magic-word 'extra' returns 'extra'
Of course, it'll "fail" miserably with values like '1,345', and will probably roll right over octal notation, treating it as though it were decimal notation (depending on the JavaScript engine?), but it could be tweaked to handle those situations as well, but really, you're better off with the regex.

If condition with && precedence not working

Code:
if (!IDTextField.value && !FirstNameField.value &&
!LastNameField.value && !DateOfBirthField.value!GenderField.value) {
alert('No criteria Added');
return;
}
The alert is not called when all the text fields are blank.

You're missing the && between the last two criteria
It should be:
if (!IDTextField.value && !FirstNameField.value &&
!LastNameField.value && !DateOfBirthField.value && !GenderField.value)
In cases like this, it makes a lot of sense to format your if statement like this:
if ( !IDTextField.value
&& !FirstNameField.value
&& !LastNameField.value
&& !DateOfBirthField.value
&& !GenderField.value)
If you do it this way, you can't make the mistake you just made.

xbonez got it right. You are missing && between last two expression.
For something not so important, I would like to get all expressions evaluated using || and then add negation using !, rather than negating all expression and evaluate them with &&. This can make this expression a little faster, if am not wrong.
if (!(IDTextField.value || FirstNameField.value ||
LastNameField.value || DateOfBirthField.value || GenderField.value)) {
alert('No criteria Added');
return;
}
Tell me what you all think??

What is this little abomination?
... !DateOfBirthField.value!GenderField.value
I think that should be:
... !DateOfBirthField.value && !GenderField.value

You should write your code like this
if (!IDTextField.value && !FirstNameField.value &&
!LastNameField.value && !DateOfBirthField.value && !GenderField.value) {
alert('No criteria Added');
return;
}
You're missing the && between the last two criteria

the && is missed ,add it and try ,should work if no other errors exist