@lwc/template-compiler

Compile LWC HTML template for consumption at runtime.

Installation

yarn add --dev @lwc/template-compiler

Usage

import compile from '@lwc/template-compiler';

const options = {};
const { code, warnings } = compile(
    `
    <template>
        <h1>Hello World!</h1>
    </template>
`,
    options
);

for (let warning of warnings) {
    console.log(warning.message);
}

console.log(code);

APIs

compile

Compile a LWC template to javascript source code consumable by the engine.

import compile from '@lwc/template-compiler';
const { code, warnings } = compile(`<template><h1>Hello World!</h1></template>`, {});

Parameters:

• source (string, required) - the HTML template source to compile.
• options (object, required) - the options to used to compile the HTML template source.

Options:

• experimentalComputedMemberExpression (boolean, optional, false by default) - set to true to enable computed member expression in the template, eg: {list[0].name}.
• experimentalDynamicDirective (boolean, optional, false by default) - set to true to allow useges of lwc:dynamic directive in the template.
• preserveHtmlComments (boolean, optional, false by default) - set to true to disable the default behavior of stripping HTML comments.

Return: The method returns an object with the following fields:

• code (string) - the compiled template.
• warnings (array) - the list of warnings produced when compiling the template. Each warning has the following fields:
  • message (string) - the warning message.
  • level (string) - the severity of the warning: info, warning, error.
  • start (number) - the start index in the source code producing the warning.
  • length (number) - the character length in the source code producing the warning.

compileToFunction

Compile a LWC template to a javascript function. This method is mainly used for testing purposes.

import { LightningElement } from 'lwc';
import { compileToFunction } from '@lwc/template-compiler';

const html = compileToFunction(`<template><h1>Hello World!</h1></template>`);

class Component extends LightningElement {
    render() {
        return html;
    }
}

Parameters:

• source (string, required) - the HTML template source to compile.

Return: The method returns an evaluated function that can be used directly in a component render method.