How to implement not with if statement in Ember Handlebars?

Question

I have a statement like this:

{{#if IsValid}}

I want to know how I can use a negative if statement that would look like that:

Answer 1

Below Statements Will help full if you want to use if and else :

{{#if author}}
    
{{firstName}} {{lastName}}
{{else}}
    
Unknown Author
{{/if}}

NOTE : Dont close the if Block until logic finished ...