hastToHtml()

Serialize a HAST root node into an HTML string.

import { hastToHtml } from "@unifast/core";

Signature

function hastToHtml(hast: HastRoot): string

Parameters

hast

PropertyTypeDefaultDescription
type"root"—Node type identifier
childrenHastNode[]—Child nodes of the tree

Returns

string — The serialized HTML string.

Usage

import { hastToHtml } from "@unifast/core";
import type { HastRoot } from "@unifast/core";

const hast: HastRoot = {
  type: "root",
  children: [
    {
      type: "element",
      tagName: "h1",
      properties: { id: "hello", className: ["title", "main"] },
      children: [
        { type: "text", value: "Hello " },
        {
          type: "element",
          tagName: "strong",
          properties: {},
          children: [{ type: "text", value: "world" }],
        },
      ],
    },
  ],
};

const html = hastToHtml(hast);

console.log(html);
// <h1 class="title main" id="hello">Hello <strong>world</strong></h1>

Examples

Basic serialization

import { hastToHtml } from "@unifast/core";
import type { HastRoot } from "@unifast/core";

const hast: HastRoot = {
  type: "root",
  children: [
    {
      type: "element",
      tagName: "p",
      properties: {},
      children: [
        { type: "text", value: "This is " },
        {
          type: "element",
          tagName: "strong",
          properties: {},
          children: [{ type: "text", value: "bold" }],
        },
        { type: "text", value: " text." },
      ],
    },
  ],
};

console.log(hastToHtml(hast));
// <p>This is <strong>bold</strong> text.</p>

Void elements

Void elements (<br>, <img>, <hr>, etc.) are self-closed automatically:

import { hastToHtml } from "@unifast/core";
import type { HastRoot } from "@unifast/core";

const hast: HastRoot = {
  type: "root",
  children: [
    {
      type: "element",
      tagName: "img",
      properties: { src: "photo.jpg", alt: "A photo" },
      children: [],
    },
  ],
};

console.log(hastToHtml(hast));
// <img alt="A photo" src="photo.jpg" />

With compile() output

import { compile } from "@unifast/node";
import { hastToHtml } from "@unifast/core";
import type { HastRoot } from "@unifast/core";

const result = compile("**bold text**", { outputKind: "hast" });
const hast: HastRoot = JSON.parse(result.output as string);

console.log(hastToHtml(hast));
// <p><strong>bold text</strong></p>

Raw HTML passthrough

import { hastToHtml } from "@unifast/core";
import type { HastRoot } from "@unifast/core";

const hast: HastRoot = {
  type: "root",
  children: [
    { type: "raw", value: "<div class=\"custom\">Raw HTML</div>" },
  ],
};

console.log(hastToHtml(hast));
// <div class="custom">Raw HTML</div>

Behavior

  • HTML escaping: Text content is escaped (&, <, >, ")

  • Void elements: area, base, br, col, embed, hr, img, input, link, meta, param, source, track, wbr are self-closed

  • Attributes: Sorted alphabetically; className arrays are joined with spaces and rendered as class; boolean true renders as bare attribute; false/null/undefined are omitted

  • Comments: Rendered as <!--value-->

  • Doctype: Rendered as <!DOCTYPE html>

  • Raw nodes: Output as-is without escaping