RenderContext

RenderContext is responsible for resource management and HTML generation during Server-Side Rendering, providing module dependency collection and resource injection order constraints.

Usage

Get an instance through esmx.render():

src/entry.node.ts

async server(esmx) {
    const server = http.createServer((req, res) => {
        esmx.middleware(req, res, async () => {
            const rc = await esmx.render({
                params: {
                    url: req.url
                }
            });
            res.end(rc.html);
        });
    });
}

Main Features

Dependency Collection

RenderContext collects module and resource dependencies during component rendering, avoiding preloading all resources.

On-Demand Collection

Automatically tracks and records module dependencies during actual component rendering
Only collects CSS, JavaScript, and other resources actually used in the current page rendering
Precisely records module dependency relationships for each component through importMetaSet
Supports dependency collection for async components and dynamic imports

Automated Processing

Developers don't need to manually manage the dependency collection process
The framework automatically collects dependency information during component rendering
Uniformly processes all collected resources through the commit() method
Automatically handles circular dependencies and duplicate dependencies

Performance Optimization

Avoids loading unused modules, significantly reducing first-screen loading time
Precisely controls resource loading order, optimizing page rendering performance
Automatically generates optimal Import Maps
Supports resource preloading and on-demand loading strategies

Resource Injection

RenderContext provides multiple methods to inject different types of resources, each carefully designed to optimize resource loading performance:

preload(): Preloads CSS and JS resources, supports priority configuration
css(): Injects first-screen stylesheets, supports critical CSS extraction
importmap(): Injects module import maps, supports dynamic path resolution
moduleEntry(): Injects client entry module, supports multi-entry configuration
modulePreload(): Preloads module dependencies, supports on-demand loading strategy

Resource Injection Order

RenderContext strictly controls resource injection order. This order design is based on browser working principles and performance optimization considerations:

head section:
- preload(): Preloads CSS and JS resources, letting the browser discover and start loading these resources as early as possible
- css(): Injects first-screen stylesheets, ensuring page styles are in place when content renders
body section:
- importmap(): Injects module import maps, defining ESM module path resolution rules
- moduleEntry(): Injects client entry module, must be executed after importmap
- modulePreload(): Preloads module dependencies, must be executed after importmap

Complete Rendering Flow

A typical flow is as follows:

src/entry.server.ts

export default async (rc: RenderContext) => {
    const app = createApp();
    const html = await renderToString(app, {
       importMetaSet: rc.importMetaSet
    });
    await rc.commit();
    rc.html = `
        <!DOCTYPE html>
        <html>
        <head>
            ${rc.preload()}
            ${rc.css()}
        </head>
        <body>
            ${html}
            ${rc.importmap()}
            ${rc.moduleEntry()}
            ${rc.modulePreload()}
        </body>
        </html>
    `;
};

Advanced Features

Base Path Configuration

RenderContext provides a flexible dynamic base path configuration mechanism, supporting dynamic setting of static resource base paths at runtime:

src/entry.node.ts

const rc = await esmx.render({
    base: '/esmx',
    params: {
        url: req.url
    }
});

This mechanism is particularly suitable for the following scenarios:

Multi-Language Site Deployment

main-domain.com      → Default language
main-domain.com/cn/  → Chinese site
main-domain.com/en/  → English site

Micro-Frontend Applications
- Supports flexible deployment of sub-applications under different paths
- Facilitates integration into different host applications

Import Map Mode

RenderContext provides two Import Map modes:

Inline Mode (default)
- Embeds import map directly into HTML
- Suitable for small applications, reduces additional network requests
- Immediately available when page loads
JS Mode
- Loads import map through external JavaScript file
- Suitable for large applications, can utilize browser caching mechanism
- Supports dynamic update of mapping content

Can choose appropriate mode through configuration:

src/entry.node.ts

const rc = await esmx.render({
    importmapMode: 'js',
    params: {
        url: req.url
    }
});

Entry Function Configuration

RenderContext supports specifying the Server-Side Rendering entry function through the entryName configuration:

src/entry.node.ts

const rc = await esmx.render({
    entryName: 'mobile',
    params: {
        url: req.url
    }
});

This mechanism is particularly suitable for the following scenarios:

Multi-Template Rendering

src/entry.server.ts

   // Mobile entry function
   export const mobile = async (rc: RenderContext) => {};

   export const desktop = async (rc: RenderContext) => {};

A/B Testing
- Supports using different rendering logic for the same page
- Facilitates user experience experiments
- Flexibly switch different rendering strategies
Special Rendering Requirements
- Supports certain pages using custom rendering processes
- Adapts to performance optimization needs of different scenarios
- Implements more fine-grained rendering control

Best Practices

Get RenderContext Instance
- Always get instance through the esmx.render() method
- Pass appropriate parameters as needed
- Avoid manually creating instances
Dependency Collection
- Ensure all modules correctly call importMetaSet.add(import.meta)
- Call commit() method immediately after rendering completes
- Reasonably use async components and dynamic imports to optimize first-screen loading
Resource Injection
- Strictly follow resource injection order
- Don't inject CSS in body
- Ensure importmap comes before moduleEntry
Performance Optimization
- Use preload to preload critical resources
- Reasonably use modulePreload to optimize module loading
- Avoid unnecessary resource loading
- Utilize the browser caching mechanism to optimize loading performance

#RenderContext

#Usage

#Main Features

#Dependency Collection

#On-Demand Collection

#Automated Processing

#Performance Optimization

#Resource Injection

#Resource Injection Order

#Complete Rendering Flow

#Advanced Features

#Base Path Configuration

#Import Map Mode

#Entry Function Configuration

#Best Practices

#RenderContext

#Usage

#Main Features

#Dependency Collection

#On-Demand Collection

#Automated Processing

#Performance Optimization

#Resource Injection

#Resource Injection Order

#Complete Rendering Flow

#Advanced Features

#Base Path Configuration

#Import Map Mode

#Entry Function Configuration

#Best Practices

RenderContext

Usage

Main Features

Dependency Collection

On-Demand Collection

Automated Processing

Performance Optimization

Resource Injection

Resource Injection Order

Complete Rendering Flow

Advanced Features

Base Path Configuration

Import Map Mode

Entry Function Configuration

Best Practices

RenderContext

Usage

Main Features

Dependency Collection

On-Demand Collection

Automated Processing

Performance Optimization

Resource Injection

Resource Injection Order

Complete Rendering Flow

Advanced Features

Base Path Configuration

Import Map Mode

Entry Function Configuration

Best Practices