Declarations

Inside @hg blocks, use JavaScript-like declarations to bind template variables.

const and let

<!--
@hg
const text = "foo bar"
let mutable = "original"
@endhg
-->

- {{ text }}
- {{ mutable }}

Reassignment

<!--
@hg
let foo = "before"
foo = "after"
@endhg
-->

{{ foo }}

Objects and arrays

<!--
@hg
const object = {
  animal: "duck",
  state: "sitting",
}
const list = ["apple", "banana"]
@endhg
-->

- {{ object.animal }} is {{ object.state }}
- {{ list[0] }}

Template literals

Backtick strings with ${expression} are allowed. Expressions inside ${} follow the same whitelist as {{ }}:

<!--
@hg
const name = "world"
const msg = `hello ${name}`
@endhg
-->

{{ msg }}

Component calls are not allowed inside template literal expressions.

Allowed updates

• ++ / -- (prefix and postfix)
• Compound assignment: +=, -=, *=, /=

Not allowed

• function declarations and arrow functions
• import / require
• Destructuring assignment
• try / catch, new

Reserved words (if, each, include, etc.) cannot be used as identifiers. See Hyogen blocks.