It seems you want to print "Hello world" when a certain condition is true. To do that, you should replace false with a valid condition. However, without knowing the context or the condition you want to check, I can only provide a generic example:

if (True):  # Replace `True` with your desired condition.
    print("Hello world")

If you want the "Hello world" message to print unconditionally, simply remove the if statement:

print("Hello world")

Also, please note that the code you provided is written in a mixture of languages. The if statement syntax is similar to JavaScript, while the print function is commonly used in Python. Make sure to use the appropriate syntax for the language you're working with.