Field presence

{if entry has 'excerpt'}
  <p class="excerpt">{'excerpt'}</p>
{endif}

Multiple fields:

{if entry has 'price' and 'value' and 'size'}
  …
{endif}

Existence of a named entry

{if 'site_elements'.'hero' exist}
  {from 'site_elements' get entry 'hero'}
    <section class="hero">{'content'}</section>
  {endget}
{endif}

Both collection and entry are quoted. Prefer this over the older unquoted site_elements.hero form.

Fallback image

{if entry has 'featured_image'}
  <img src="{'featured_image'}" alt="{title}">
{else}
  <img src="/images/placeholder.jpg" alt="">
{endif}

Comparisons

{if entry has 'price' <= 15}
  <span class="badge">Deal</span>
{endif}

{if entry 'price' <= 15}
  …
{endif}

{if current.language = 'de'}
  <p>Willkommen!</p>
{else}
  <p>Welcome!</p>
{endif}

Prefer single = for equality.

if … or … else

{if entry has 'price' <= 15 or entry has 'discount'}
  <p>On sale</p>
{else}
  <p>Standard price</p>
{endif}

Inside loops

{for each entry in 'blog' with status = published ordered by newest}
  <h2>{title}</h2>
  {if entry has 'excerpt'}
    <p>{'excerpt'}</p>
  {endif}
{endfor}