How to implement not with if statement in Ember Handlebars?

Question

Simple answers for simple questions:

{{#unless isValid}}
{{/unless}}

Also keep in mind that you can insert an {{else}} in between an {{#if}} or {{#unless}} and the closing tag.

You have many ways of doing that.

1. Use {{unless}}:

{{#unless isValid}}
  ...
{{else}}
  ...
{{/unless}}

2. Use inline-if helper:

{{#if (if isValid false true)}}
  ...
{{else}}
  ...
{{/if}}

3. Use ember-truth-helpers addon:

{{#if (not isValid)}}
  ...
{{else}}
  ...
{{/if}}

it can be done in multiple ways.

1 use unless

{{#unless IsValid}}
<Your Code>
{{/unless}}

2.use if else

{{#if IsValid}}
{{else}}
<Your Code>
{{/if}}

3.use not helper

{{#if (not IsValid)}}
<Your Code>
{{/if}}

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}}
  <h3 class="warning">WARNING</h3>
  {{/unless}}

{{#if items.length}}
    //Render
{{/if}}

Here items.length .. if it returns some value except null, then only it will enters into the if loop.

NOTE : You can check Boolean values also. In If block

{{#if booleanFloag}}