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

unless block helper (built-in helper)

unless helper is the inverse of the if helper.

Its block will be rendered if the expression returns a falsy value.

  {{#unless valid}}
  
WARNING
  {{/unless}}