Your code looks ok to me, can you share what error you get?
Here is what worked for me:
***
function greet(name="NULL")
{
if(name!="NULL")
{
console.log("Hello "+name+"! Thanks for joining us.");
}
else {
console.log("What is your name?");
}
}
// call the function
greet("Abhishek");
***

Here is the answer:
***

Login Form

Email

***

Here is the correct answer:
***
let square = function (num)
{
return num*num
};
let result = square(5);
console.log(result);
***

But JavaScript Level 5 doesn't have any lesson 7

Here is the correct answer:
***
let a = 10;
let b = 20;
let c = a + b;

console.log(c);
document.write("Hello JS!")
***

Are you accessing the content on Mobile? Then please go to the Editor Tab and then click on Next.

Here is the answer:
***

***

Thanks for pointing this out. The content has been corrected.

This should work:
***







Hello
Studytonight
Bro



***

Here is the correct answer:
***

Do you know?

Honey bees communicate by dancing.

Turtles can breathe through their !

***

Here is the correct answer:
***

Resize the browser window to see how the background color of this paragraph change on different screen sizes.

***

Here is the code:
***

Login Form

Email

***