Partial Rendering

Written for AI agents. See Log Methodology Note below for details.

Partial Rendering is when we have jay-html file and a jay-stack component has a slowly changing phase. The slowly changing phase generates Partial<ViewState> which we can use to partially render the jay-html file.

What it means is that

1. We inline all the slowly Partial<ViewState> into the jay-html
2. If we have multiple UrlParams, that is we have multiple result HTML pages for a route, we inline into each result HTML separately
3. If we have conditions that are bound to an inline member of Partial<ViewState>, we resolve the condition (delete false branches)
4. If we have forEach that are bound to an inline member of Partial<ViewState>, it is rendered as a static list
5. The inlined jay-html is used for fast rendering phase and for interactive rendering.

how it works

The component Slowly rendering phase generates a Partial<ViewState>. Given this partial view state, the jay compiler transforms the jay-html into the inlined jay html.

The jay-html includes bindings to the ViewState of different types, and each is handled in the appropriate way.

text, property and attribute bindings

Such bindings are written as {field} or {field.a.b.c} or word {field} words {fields2}....

The normal compiling generates dt(vs => vs.field) or dt(vs => vs.field?.a?.b?.c), using dp, da or dt for property, attribute or text.

It is compiled as a template of values.

Given a value, we compile the expression into a value by inlining the value. If the expression becomes static, it is handled as a static text and not a function. If there are any unbound values, it remains a function.

Given a value for field=world, the expression {field} turns into world Given a value for field=world, the expression hello {field} turns into hello world Given a value for field=world, the expression hello {field} from {geo} turns into dt(vs => 'hello world from ${vs.geo}')

conditions

Such expressions are written as member or member.a.b.c, and are normally compiled into vs => vs.member or vs => vs.member.a.b.c.

It is compiled as a condition.

Condition expressions can also use ! for not expressions, or equals to enum values, such as !member which turns into vs => !vs.member and anEnum === one which turns into vs => vs.anEnum === AnEnum.one.

Given a value for member, the condition can be resolved to a true or false value, which is then used to decide if to include the condition element tree or not.

forEach

For each iteration member, which returns the item to iterate over, normally looks like member or member.a

It is normally compiled into a function such as (member: MemberType) => member or (member: MemberType) => member?.a.

It is compiled as an accessor.

Given a value for the accessed iteration items, we can remove the forEach and instead just render the forEach items into the jay-html.

class expressions

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Log Methodology Note

Note: These design logs are written primarily for AI agents as part of the Design Log methodology and made accessible here for human readers. The language and structure are optimized for machine consumption — expect precise, specification-style prose rather than narrative documentation.