react.js every nth item add opening tag or closing

Question

I'm having trouble with this logic since react/jsx does not allow for non closing tags to be added to an array/child component. For example with bootstrap css I want to add a row for every 4 columns.

So the logic is as follows:

Add a opening row ex: <div className="row">, then loop inside this row and every loop append a column ex: <div className="column>{this.data}</div> when the loop reaches 4 check with if(i % 4 == 0) and add a closing </div> tag while adding new row tag <div className="row">;

The code below would work in another language but in react this is not doable since we push a closing tag and a opening tag (which is invalid jsx):

generateColumns(columns) {
 let newColumns = [];

 columns.forEach(function(column, idx) {
  newColumns.push( <div className="column"> some data </div> );

  if (idx % 4 == 0) {
   // Here we end the row and start a new row, works in any other language.
   newColumns.push( </div> <div className="row"> );
  }
 });

 // This array now has the proper tags for opening a row every 4th item and closing it.
 return newColumns;
},
render() {
   return (
     <div className="row">
       {this.generateColumns(this.props.columns)}
     </div>
   )
}

The expected output would be:

<div class="row">
  <div class="column">
   Some data
  </div>
  <div class="column">
   Some more data
  </div>
  <div class="column">
   Other data
  </div>
  <div class="column">
   Something else
  </div>
</div>
<div class="row">
  <div class="column">
   Some data
  </div>
  <div class="column">
   Some more data
  </div>
  <div class="column">
   Other data
  </div>
  <div class="column">
   Something else
  </div>
</div>

//the above would be repeated and new rows would appear every 4 columns.

Answer 1

render() {
   const rows = array_chunk(this.props.columns, 4)
   return (
     {
       rows.map((row) => (
         <div className="row">
         {
           row.map((col) => (
             <div className="col">{ col }</div>
           ))
         }
         </div>
       ))
     }
   )
}

An example array_chunk (I recommend that you use lodash)

module.exports = function chunks(arr, size) {
  if (!Array.isArray(arr)) {
    throw new TypeError('Input should be Array');
  }

  if (typeof size !== 'number') {
    throw new TypeError('Size should be a Number');
  }

  var result = [];
  for (var i = 0; i < arr.length; i += size) {
    result.push(arr.slice(i, size + i));
  }

  return result;
};

Answer 2

I actually just used arrays and react handled fine the rendering.

render() {
    let rows = [],
        cols = []
    let index = 0
    const totalCols = 20;

    for (index; index < totalCols; index++) {
        cols.push(<div class="col" key={index}/>)
        if ((index + 1) % 4 == 0) {
            rows.push(
                <div class="row" key={index}>
                    {cols}
                </div>
            )
            cols = []
        }
    }
    return (
        <div class="container">
            {rows}
        </div>
    )
}