gistfile1.ts

import sax = require('sax');

/**
 * Beautify HTML for human
 */
export function beautify(html: string) {
  return new Promise((resolve, reject) => {
    const parser = sax.parser(false, {});

    let indent = 0;
    let result = '';

    parser.onopentag = function (tag) {
      if (isSelfClosing(tag.name)) {
        result += `${getTabs(indent)}<${tag.name.toLowerCase()}${getAttrs(tag.attributes)}/>\n`;
      } else {
        result += `${getTabs(indent)}<${tag.name.toLowerCase()}${getAttrs(tag.attributes)}>\n`;
        indent += 1;
      }
    };
    parser.ontext = function (text) {
      // console.log('ontext', JSON.stringify(text));
    };
    parser.onscript = function (script) {
      // console.log('onscript', JSON.stringify(script));
    };
    parser.onclosetag = function (tagName) {
      if (!isSelfClosing(tagName)) {
        indent -= 1;
        result += `${getTabs(indent)}</${tagName.toLowerCase()}>\n`;
      }
    };
    parser.onerror = function (err) {
      reject(err);
    };
    parser.onend = function () {
      resolve(result);
    };

    parser.write(html);
    parser.close();
  });
}

function getTabs(n: number) {
  let i = 0;
  let r = '';
  while (i < n) {
    i += 1;
    r += '    ';
  }
  return r;
}

function getAttrs(attributes: {[key: string]: string | sax.QualifiedAttribute}) {
  const res: string[] = [];
  for (const attr of Object.keys(attributes)) {
    res.push(`${attr.toLowerCase()}="${quoteEscape(attributes[attr] as string)}"`);
  }
  return res.length ? ' ' + res.join(' ') : '';
}

function isSelfClosing(tagName: string) {
  return ['IMG'].indexOf(tagName) > -1;
}

const HTML_ENTITY_MAP: {[key: string]: string} = {
  '"': 'quot',
  '&': 'amp'
};

function quoteEscape(html: string) {
  return html.replace(/["&]/g, (s) => {
    return `&${HTML_ENTITY_MAP[s]};`;
  });
}