Basics

Last updated 8 months ago

Jael syntax is a superset of HTML. The following is valid both in HTML and Jael:

<!DOCTYPE html>
<html>
<head>
<title>Title</title>
</head>
<body>
<h1>Hello!</h1>
</body>
</html>

However, Jael adds two major changes.

Interpolation

Firstly, text blocks can contain interpolations, which are merely Dart expression contained in double curly braces ({{ }}). The value within the braces, once evaluated will be HTML escaped, to prevent XSS. To achieve unescaped output, append a hyphen (-) to the first brace ({{- }}).

<div>
{{ user.name }}
</div>
<!-- Do not HTML escape this: -->
<div>
{{- raw.data.will.not.be('escaped') }}
</div>

Attributes

Secondly, whereas in HTML, the values of attributes can only be strings, Jael allows for their values to be any Dart expression:

<img src=profile.avatar ?? "http://example.com/img/avatars/default.png">
<a class=['btn', 'ban-default', 'btn-lg']>Link</a>
<p style={'color': 'red'}></p>

Attribute Values

Values are handled as such:

  • Maps: Serialized as though they were style attributes.

  • Iterables: Joined by a space, like class attributes.

  • Anything else: toString() is invoked.

Quoted Attribute Names

In case the name of your attribute is not a valid Dart identifier, you can wrap it with quotes, and it will still be processed as per normal:

<button "(click)"="myEventHandler($event)" />

Unescaped Attributes

These will also be HTML escaped; however, you can replace = with != to print unescaped text:

<img src!="<SCARY XSS STRING BEWARE!!!>" />