table2json.js

/*****************************************************************************
 *
 * table to json
 *
*****************************************************************************/
(function() {
  HTMLTableElement.prototype.toJSON = toJSON;
  HTMLTableElement.prototype.toArray = toArray;

  function toJSON(indent,fn,headers)
  {
    return JSON.stringify(this.toArray(fn,headers),null,indent);
  }

  // fn: filter function. prototype: function fn(v); 
  // in filter function this point to HTMLTableCellElement
  function toArray(fn,headers)
  {
    if(!(this instanceof HTMLTableElement))
      throw new Error('not table element');

    const oTable = this;

    let heads = [];
    let rows = [];
    let excludes = new Set;

    if(headers instanceof Array && headers.length > 0)
    {
      heads = headers;
    }
    else
    {
      let oThead = oTable.tHead;
      if(!oThead)
        throw new Error('thead element not found');

      let oTR = oThead.querySelector('thead > tr');
      oTR.querySelectorAll('tr > *').forEach(el => heads.push('key' in el.dataset && el.dataset.key.length > 0 ? el.dataset.key : el.innerText.trim().replace(/[\r\n]/g,'')));
    }

    let oTbodies = oTable.tBodies;
    if(oTbodies.length == 0)
      throw new Error('tbody element not found');

    let oTbody = oTbodies[0];
    let filter = fn || (v => v);


    oTbody.querySelectorAll('tbody > tr').forEach((el,r) => {
      let row = rows[r] === undefined ? {} : rows[r];

      let oTDs = el.querySelectorAll('tr > *');
      let columnnum = heads.length;

      for(let c=0,h=0;c<columnnum;c++,h++)
      {
        while(heads[h] in row)
          h++;

        let td = oTDs.item(c);
        if(!td)
          continue;

        let colspan = parseInt(td.getAttribute('colspan')) || 1;
        let rowspan = parseInt(td.getAttribute('rowspan')) || 1;
        let cellText = filter.call(td,td.innerText.trim()); 

        if(h < heads.length && !(heads[h] in row))
          row[heads[h]] = cellText;

        if(rowspan > 1)
        {
          for(let i=1;i<rowspan;i++)
          {
            if(rows[r+i] === undefined)
              rows[r+i] = {};

            rows[r+i][heads[h]] = cellText;
          }
        }

        if(colspan > 1)
          h+=(colspan - 1);
      };
      if(rows[r] === undefined)
        rows[r] = row;
      
      if('exclude' in el.dataset && el.dataset.exclude === 'true')
        excludes.add(r);

    });
    
    return rows.filter((v,i) => !excludes.has(i));
  }
})();