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Merge table rows using JavaScript

Tags:

javascript

html

css

I am using a normal table, here is my requirement:

If a table row values duplicate it should get merged using javascript.For eg: table 1 row values and table2 row values are same then it should get merged and the value should be displayed only once using javascript. Here I will attach my codings.

function myFunction() {
  const firstRows = { };
  let shade = false;
  
  const colsToMerge = [0, 1];

  Array.from(document.querySelectorAll('tbody tr')).forEach(tr => {
    const text = tr.children[0].innerText;
    if (!(text in firstRows)) {
      firstRows[text] = { shade, elem: tr, count: 1 };
      shade = !shade;
    } else {
      const firstRow = firstRows[text]
      firstRow.count++;
      colsToMerge.forEach(i => tr.children[i].remove());
      colsToMerge.forEach(i =>
        firstRow.elem.children[i]
                .setAttribute('rowspan', firstRow.count)
      );
    }
    if (firstRows[text].shade) tr.classList.add('dark');
  });
}
table {
  font-family: arial, sans-serif;
  border-collapse: collapse;
  width: 100%;
}

th {
  background: #a9a9a9;
}

td,
th {
  border: 1px solid #dddddd;
  text-align: center;
  padding: 8px;
  font-family: monospace;
  font-size: 17px;
}

.dark {
  background-color: #dddddd;
}
<body onload="myFunction()">
  <table>
    <tr>
      <th>Company</th>
      <th>Contact</th>
      <th>Country</th>
    </tr>
    <tbody>
      <tr>
        <td>Alfreds Futterkiste</td>
        <td>Maria Anders</td>
        <td>Germanyindgo</td>
      </tr>
      <tr>
        <td>Alfreds Futterkiste</td>
        <td>Maria Anders</td>
        <td>Germany</td>
      </tr>
      <tr>
        <td>Centro comercial Moctezuma</td>
        <td>Francisco Chang</td>
        <td>Mexico</td>
      </tr>
      <tr>
        <td>Ernst Handel</td>
        <td>Roland Mendel</td>
        <td>Austria</td>
      </tr>
      <tr>
        <td>Island Trading</td>
        <td>Helen Bennett</td>
        <td>UK</td>
      </tr>
      <tr>
        <td>Laughing Bacchus Winecellars</td>
        <td>Yoshi Tannamuri</td>
        <td>Canada</td>
      </tr>
      <tr>
        <td>Magazzini Alimentari Riuniti</td>
        <td>Giovanni Rovelli</td>
        <td>Italy</td>
      </tr>
    </tbody>
  </table>
</body>

Check this table

like image 668
Thirshal Avatar asked Apr 22 '26 22:04

Thirshal

2 Answers

Here is a working solution for dynamically merging consecutive row cells in every column.

The solution also works for toggling the shade and will only toggle the shade when a 'full' row starts, which is, when there is no merging between consecutive rows.

Also, you have to wrap the tr in the table header in a thead as that can cause problems with document.querySelectorAll('tbody tr') event tbody is specified in the query.

I slightly modified the table to show the shading and merging: enter image description here

function myFunction() {
  const previousRow = {};
  const colsChanged = {};
  let dark = false;

  Array.from(document.querySelectorAll('tbody tr')).forEach((tr, rowIdx) => {
    Array.from(tr.children).forEach((td, colIdx) => {
      if (rowIdx > 0 && previousRow[colIdx].text === td.innerText) {
        previousRow[colIdx].elem.setAttribute('rowspan', ++previousRow[colIdx].span);
        colsChanged[colIdx] = false;
        td.remove();
      } else {
        previousRow[colIdx] = { span: 1, text: td.innerText, elem: td, dark };
        colsChanged[colIdx] = true;
      }
    });
    const rowChanged = Object.values(colsChanged).every(Boolean);
    dark = rowChanged && rowIdx > 0 ? !dark : dark;
    if (dark) {
      tr.classList.add('dark');
    }
  });
}
table {
  font-family: arial, sans-serif;
  border-collapse: collapse;
  width: 100%;
}

th {
  background: #a9a9a9;
}

td,
th {
  border: 1px solid black;
  text-align: center;
  padding: 8px;
  font-family: monospace;
  font-size: 17px;
}

.dark {
  background-color: #dddddd;
}
<body onload="myFunction()">
  <table>
    <thead>
      <tr>
        <th>Company</th>
        <th>Contact</th>
        <th>Country</th>
      </tr>
    </thead>
    <tbody>
      <tr>
        <td>Alfreds Futterkiste</td>
        <td>Maria Anders</td>
        <td>Germanyindgo</td>
      </tr>
      <tr>
        <td>Alfreds Futterkiste</td>
        <td>Maria Anders</td>
        <td>Germany</td>
      </tr>
      <tr>
        <td>Centro comercial Moctezuma</td>
        <td>Francisco Chang</td>
        <td>Mexico</td>
      </tr>
      <tr>
        <td>Ernst Handel</td>
        <td>Francisco Chang</td>
        <td>Austria</td>
      </tr>
      <tr>
        <td>Ernst Handel</td>
        <td>Helen Bennett</td>
        <td>UK</td>
      </tr>
      <tr>
        <td>Laughing Bacchus Winecellars</td>
        <td>Yoshi Tannamuri</td>
        <td>Canada</td>
      </tr>
      <tr>
        <td>Magazzini Alimentari Riuniti 1</td>
        <td>Giovanni Rovelli 1</td>
        <td>Italy</td>
      </tr>
      <tr>
        <td>Magazzini Alimentari Riuniti 2</td>
        <td>Giovanni Rovelli 2</td>
        <td>Italy</td>
      </tr>
      <tr>
        <td>Magazzini Alimentari Riuniti 3</td>
        <td>Giovanni Rovelli 3</td>
        <td>Italy</td>
      </tr>
    </tbody>
  </table>
</body>

According to the comments below, if you want to merge cells to the right only if the corresponding cells were merged in the first column, here is a modification to do it.

a leftMerged variable is used to keep track of whether the first cell on the current line was merged to the previous one, and if so, this enables us to merge the following cells to the right if necessary. The variable is reset to false at the beginning of each line.

enter image description here

function myFunction() {
  const previousRow = {};
  const colsChanged = {};
  let leftMerged = false;
  let dark = false;

  Array.from(document.querySelectorAll('tbody tr')).forEach((tr, rowIdx) => {
    Array.from(tr.children).forEach((td, colIdx) => {
      if (rowIdx > 0 && (colIdx === 0 || leftMerged) && previousRow[colIdx].text === td.innerText) {
        previousRow[colIdx].elem.setAttribute('rowspan', ++previousRow[colIdx].span);
        colsChanged[colIdx] = false;
        td.remove();
        if (colIdx === 0) {
          leftMerged = true;
        }
      } else {
        previousRow[colIdx] = { span: 1, text: td.innerText, elem: td, dark };
        colsChanged[colIdx] = true;
      }
    });
    const rowChanged = Object.values(colsChanged).every(Boolean);
    dark = rowChanged && rowIdx > 0 ? !dark : dark;
    if (dark) {
      tr.classList.add('dark');
    }
    leftMerged = false;
  });
}
table {
  font-family: arial, sans-serif;
  border-collapse: collapse;
  width: 100%;
}

th {
  background: #a9a9a9;
}

td,
th {
  border: 1px solid black;
  text-align: center;
  padding: 8px;
  font-family: monospace;
  font-size: 17px;
}

.dark {
  background-color: #dddddd;
}
<body onload="myFunction()">
  <table>
    <thead>
      <tr>
        <th>Company</th>
        <th>Contact</th>
        <th>Country</th>
        <th>Col4</th>
        <th>Col5</th>
      </tr>
    </thead>
    <tbody>
      <tr>
        <td>Alfreds Futterkiste</td>
        <td>Maria Anders</td>
        <td>Germanyindgo</td>
        <td>1</td>
        <td>2</td>
      </tr>
      <tr>
        <td>Alfreds Futterkiste</td>
        <td>Maria Anders</td>
        <td>Germany</td>
        <td>1</td>
        <td>2</td>
      </tr>
      <tr>
        <td>Centro comercial Moctezuma</td>
        <td>Francisco Chang</td>
        <td>Mexico</td>
        <td>1</td>
        <td>2</td>
      </tr>
      <tr>
        <td>Ernst Handel</td>
        <td>Francisco Chang</td>
        <td>Austria</td>
        <td>1</td>
        <td>2</td>
      </tr>
      <tr>
        <td>Ernst Handel</td>
        <td>Helen Bennett</td>
        <td>UK</td>
        <td>1</td>
        <td>2</td>
      </tr>
      <tr>
        <td>Laughing Bacchus Winecellars</td>
        <td>Yoshi Tannamuri</td>
        <td>Canada</td>
        <td>1</td>
        <td>2</td>
      </tr>
      <tr>
        <td>Magazzini Alimentari Riuniti 1</td>
        <td>Giovanni Rovelli 1</td>
        <td>Italy</td>
        <td>1</td>
        <td>2</td>
      </tr>
      <tr>
        <td>Magazzini Alimentari Riuniti 1</td>
        <td>Giovanni Rovelli 2</td>
        <td>Italy</td>
        <td>1</td>
        <td>2</td>
      </tr>
      <tr>
        <td>Magazzini Alimentari Riuniti 3</td>
        <td>Giovanni Rovelli 3</td>
        <td>Italy</td>
        <td>1</td>
        <td>2</td>
      </tr>
    </tbody>
  </table>
</body>
like image 92
jo_va Avatar answered Apr 24 '26 11:04

jo_va

In below snippet first I read data from table to js array, then merge rows with similar first column, and generate new html content of table body

let readTable = (tbody) => [...tbody.rows].map(row=>[...row.cells].map(c=>c.innerText));    

function mergeRows(data) {
  let h={};
  data.forEach((r,i)=> { // merge by first column
      let p=h[r[0]];
      if(p) { p[1].push(r[1]); p[2].push(r[2]) };
      if(!p) { h[r[0]]=[r[0],[r[1]],[r[2]],i]}         
  });     
  let result=Object.values(h).sort((a,b)=>a[3]-b[3]);  
  result.forEach(r=> {r[1]=[... new Set(r[1])]; r[2]=[... new Set(r[2])]}); // remove duplicates in seconond and third column
  return result;
}

function genTable(rows, tbody) {    
  let b="",x="";
  rows.forEach(r=> {
    x=r.map((c,i) => `<td>${c}</td>`).slice(0,3);
    b+=`<tr>${x.join('')}</tr>`;
  })
  tbody.innerHTML=b;
  console.log({b,rows, tbody});
}

function myFunction() {
  let table=document.querySelector('table');
  let tbody=table.tBodies[table.tBodies.length-1]; 
  genTable( mergeRows(readTable(tbody)), tbody );
}
table {
  font-family: arial, sans-serif;
  border-collapse: collapse;
  width: 100%;
}

th {
  background: #a9a9a9;
}

td,
th {
  border: 1px solid #dddddd;
  text-align: center;
  padding: 8px;
  font-family: monospace;
  font-size: 17px;
}

.dark {
  background-color: #dddddd;
}
<body onload="myFunction()">
  <table>
    <tr>
      <th>Company</th>
      <th>Contact</th>
      <th>Country</th>
    </tr>
    <tbody>
      <tr>
        <td>Alfreds Futterkiste</td>
        <td>Maria Anders</td>
        <td>Germanyindgo</td>
      </tr>
      <tr>
        <td>Alfreds Futterkiste</td>
        <td>Maria Anders</td>
        <td>Germany</td>
      </tr>
      <tr>
        <td>Centro comercial Moctezuma</td>
        <td>Francisco Chang</td>
        <td>Mexico</td>
      </tr>
      <tr>
        <td>Ernst Handel</td>
        <td>Roland Mendel</td>
        <td>Austria</td>
      </tr>
      <tr>
        <td>Island Trading</td>
        <td>Helen Bennett</td>
        <td>UK</td>
      </tr>
      <tr>
        <td>Laughing Bacchus Winecellars</td>
        <td>Yoshi Tannamuri</td>
        <td>Canada</td>
      </tr>
      <tr>
        <td>Magazzini Alimentari Riuniti</td>
        <td>Giovanni Rovelli</td>
        <td>Italy</td>
      </tr>
    </tbody>
  </table>
</body>
like image 20
Kamil Kiełczewski Avatar answered Apr 24 '26 10:04

Kamil Kiełczewski
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