TemplateCompiler API reference for the TemplateCompiler class in Semantic UI Templating code Guide

TemplateCompiler

The TemplateCompiler class is responsible for compiling template strings into an Abstract Syntax Tree (AST). This precompilation step enables efficient rendering and updates, especially useful for server-side rendering (SSR) and advanced use cases.

Constructor

Syntax

new TemplateCompiler(templateString)

Parameters

NameTypeDescription
templateStringstringThe template string to compile

Usage

import { TemplateCompiler } from '@semantic-ui/templating';


const compiler = new TemplateCompiler('<div>{{name}}</div>');

Methods

compile

Compiles the template string into an Abstract Syntax Tree (AST).

Syntax

compiler.compile()

Returns

Object - The compiled [AST]](/api/templating/ast) representation of the template.

Usage

const ast = compiler.compile();
console.log(ast);

parseTemplateString

Parses a template string, typically used for partial templates or snippets.

Syntax

TemplateCompiler.parseTemplateString(expression)

Parameters

NameTypeDescription
expressionstringThe template string to parse

Returns

Object - An object containing parsed template information.

Usage

const templateInfo = TemplateCompiler.parseTemplateString('{{> partialName data1=value1 data2=value2}}');
console.log(templateInfo);

detectSyntax

Detects whether the template uses single {} or double {{}} bracket syntax.

Syntax

TemplateCompiler.detectSyntax(templateString)

Parameters

NameTypeDescription
templateStringstringThe template string to analyze

Returns

string - Either 'singleBracket' or 'doubleBracket'.

Usage

const syntax = TemplateCompiler.detectSyntax('{{name}}');
console.log(syntax); // 'doubleBracket'

preprocessTemplate

Preprocesses the template string, handling special cases like self-closing web component tags.

Syntax

TemplateCompiler.preprocessTemplate(templateString)

Parameters

NameTypeDescription
templateStringstringThe template string to preprocess

Returns

string - The preprocessed template string.

Usage

const processed = TemplateCompiler.preprocessTemplate('<ui-icon icon="foo" />');
console.log(processed); // '<ui-icon icon="foo"></ui-icon>'

optimizeAST

Optimizes the compiled AST by joining neighboring HTML nodes.

Syntax

TemplateCompiler.optimizeAST(ast)

Parameters

NameTypeDescription
astObject[]The AST to optimize

Returns

Object[] - The optimized AST.

Usage

const optimizedAST = TemplateCompiler.optimizeAST(ast);

Server Side Compilations

You can precompile your templates on the serve then load them on the client using modern build tooling like esbuild or rollup and JSON imports.

Server

On the server we want to render our templates to an AST.

import { TemplateCompiler } from '@semantic-ui/templating';
import fs from 'fs/promises';
import path from 'path';
import { fileURLToPath } from 'url';


const __dirname = path.dirname(fileURLToPath(import.meta.url));


async function precompileTemplates(templateName) {
  const templatePath = path.join(__dirname, 'templates', `${templateName}.html`);
  const outputPath = path.join(__dirname, 'ast', `${templateName}.json`);


  const template = await fs.readFile(templatePath, 'utf-8');
  const compiler = new TemplateCompiler(template);
  const ast = compiler.compile();


  await fs.writeFile(outputPath, JSON.stringify(ast, null, 2));
}
// somewhere else
precompileTemplates('user-profile');

Client

Then on the client we can import that files directly as JSON file directly and pass as the ast parameter in defineComponent.

import { defineComponent } from '@semantic-ui/component';
import ast from './ast/user-profile.json' assert { type: 'json' };


export function defineUserProfile() {
  defineComponent({
    tagName: 'user-profile',
    ast,
    // rest of component
  });
}