Javascript “Not equal to” feature from a prompt

I am a very very beginner in Javascript and am trying to use only very basics. I am trying to only allow two certain words to be accepted into a variable prompt. If anything else other than the two allowed words are entered, I want to display a message saying only the two words are allowed, and to try again until it’s correct. This is the code I am working with so far. Everything is working well until the last section

console.log("Start of the program");

var letters = /^[a-zA-Z]*$/;

var number= prompt ("Which number between 1 and 30 do you want to translate?");
    
    while (number <1) {
        alert("Please type an integer number between 1 and 30");
        var number= prompt ("Which number between 1 and 30 do you want to translate?");
}
    while (number >30) { 
        alert("Please type an integer number between 1 and 30");
        var number= prompt ("Which number between 1 and 30 do you want to translate?");
}

    while (letters.test(number)) {
        alert("Please use digits");
        var number= prompt ("Which number between 1 and 30 do you want to translate?");
}

if (number => 1 && number <= 30) {
    var lang= prompt ("Which language do you want to translate into, French or German?");
}
while(lang != "French" != "German") {
    alert("Only French or German is allowed");
    var lang= prompt ("Which language do you want to translate into, French or German?");
}

JavaScript
​x
 
console.log("Start of the program");
​
var letters = /^[a-zA-Z]*$/;
​
var number= prompt ("Which number between 1 and 30 do you want to translate?");
    
    while (number <1) {
        alert("Please type an integer number between 1 and 30");
        var number= prompt ("Which number between 1 and 30 do you want to translate?");
}
    while (number >30) { 
        alert("Please type an integer number between 1 and 30");
        var number= prompt ("Which number between 1 and 30 do you want to translate?");
}
​
    while (letters.test(number)) {
        alert("Please use digits");
        var number= prompt ("Which number between 1 and 30 do you want to translate?");
}
​
if (number => 1 && number <= 30) {
    var lang= prompt ("Which language do you want to translate into, French or German?");
}
while(lang != "French" != "German") {
    alert("Only French or German is allowed");
    var lang= prompt ("Which language do you want to translate into, French or German?");
}
​

Even if I enter “French” or “German” I still receive the “Only French or German is allowed” alert continuously. If I change the “while (lang !=)” to an “if (lang !=)” I receive the alert once regardless of if French or German has been correctly used, and then the program continues. I also would like it to not be case sensitive (accept French, french, FRENCH etc.) in my result which uses this code currently

if (number == 1 && lang == "French") {
        alert("The translation is " +frenchNumbers[1]);

JavaScript
 
if (number == 1 && lang == "French") {
        alert("The translation is " +frenchNumbers[1]);
​

Any help would be much appreciated

Thanks, Brad

Answer

You’re missing && lang here:

while(lang != "French" && lang != "German")

JavaScript (nor any other language I’m currently aware of) allows you to compare a variable to two different values like this, without using a boolean operator and then repeating the name of the variable.

Interestingly enough, lang != "French" != "German" is valid syntax, but it doesn’t mean what you might think.

First lang != "French" is evaluated to either true or false. Then what happens next is either:

true != "German" or false != "German"

…and both of those are always true.

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Answer