extract-handlebars-context.ts

export const extract = (text: string): Object => {
  const re = /\{+\s*(.*?)\s*\}+/g;
  const tags: any[] = [];
  let matches;
  while (Boolean((matches = re.exec(text)))) {
    if (matches) {
      tags.push(matches[1]);
    }
  }
  const root: any = {};
  let context: any = root;
  const stack: any[] = [];
  const setVar = (variable: string, val: any) => {
    const numLevelsUp = (variable.match(/\\.\\./g) || []).length;
    if (numLevelsUp) {
      const v = variable.split('/').pop();
      const c = stack[stack.length - numLevelsUp];
      if (c && v) {
        c[v] = val;
      }
    } else {
      context[variable] = val;
    }
  };
  for (var tag of tags) {
    if (tag.startsWith('! ')) {
      continue;
    }
    if (tag == 'else') {
      continue;
    }
    if ('#^'.includes(tag[0]) && !tag.includes(' ')) {
      setVar(tag.substr(1), true);
      stack.push(context);
      continue;
    }
    if (tag.startsWith('#if')) {
      const vars = tag.split(' ').slice(1);
      for (const v of vars) {
        setVar(v, true);
      }
      stack.push(context);
      continue;
    }
    if (tag.startsWith('/if')) {
      context = stack.pop();
      continue;
    }
    if (tag.startsWith('#with ')) {
      const v = tag.split(' ')[1];
      var newContext = {};
      context[v] = newContext;
      stack.push(context);
      context = newContext;
      continue;
    }
    if (tag.startsWith('/with')) {
      context = stack.pop();
      continue;
    }
    if (tag.startsWith('#unless ')) {
      const v = tag.split(' ')[1];
      setVar(v, true);
      stack.push(context);
      continue;
    }
    if (tag.startsWith('/unless')) {
      context = stack.pop();
      continue;
    }
    if (tag.startsWith('#each ')) {
      const v = tag.split(' ')[1];
      const newContext = {};
      context[v] = [newContext];
      stack.push(context);
      context = newContext;
      continue;
    }
    if (tag.startsWith('/each')) {
      context = stack.pop();
      continue;
    }
    if (tag.startsWith('/')) {
      context = stack.pop();
      continue;
    }
    setVar(tag, '');
  }
  var cleanThis = (obj: any): any => {
    if (Array.isArray(obj)) {
      const acc = [];
      for (var item of obj) {
        acc.push(cleanThis(item));
      }
      return acc;
    }
    if (typeof obj == 'object' && obj.constructor == Object) {
      if (Object.keys(obj).length == 1 && obj.hasOwnProperty('this')) {
        return cleanThis(obj['this']);
      }
      const acc: any = {};
      for (var [k, v] of Object.entries(obj)) {
        acc[k] = cleanThis(v);
      }
      return acc;
    }
    return obj;
  };
  return cleanThis(root);
};