Цикл по массиву и группировка элементов по модулю - jquery

var list = ["company1", "company2", "company3", "company4", "company5", "company6"];

var itemWrapper = $('.wrapper');
itemWrapper.empty();

list.forEach(function(row, idx) {
	if (!(idx % 3)) {
  	itemWrapper.append('<div class = "row"></div');
  }
  var itemRow = $('.wrapper .row:last-child');
  itemRow.append('<div class = "col col-4">'+row+'</div>');
});

<script src = "https://code.jquery.com/jquery-3.2.1.js"></script>

<div class = "wrapper">

</div>

var list = ["company1", "company2", "company3", "company4", "company5", "company6", "company7"];

var $wrapper = $('.wrapper');
$wrapper.empty();

var $row;                                                      // the current row of elements
$.each(list, function(index, value) {
  if (index % 3 == 0) {                                         // for every three elements
    $row = $('<div class = "row"></div>').appendTo($wrapper);    // create a new row element and assign it to $row
  }
    
  $row.append('<div class = "col col-4">' + value + '</div>');   // add the current element to the current row
});

.row { margin: 10px 0; background: #eee; }

.row > * { display: inline-block; margin: 0 10px; }

<script src = "https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class = "wrapper"></div>

var list = ["company1", "company2", "company3", "company4", "company5", "company6", "company7", "company8", "company9", "company10"];

var itemWrapper = $('.wrapper');

var listChunks = [];
var chunkSize = 3;
for (var i = 0; i < list.length; i += chunkSize) {
    listChunks.push(list.slice(i,i+chunkSize));
}

itemWrapper.empty();
var rowHtmlOpen = '<div class = "row">';
var rowHtmlClose = '</div>';
listChunks.forEach(function (chunk) {
    var rowHtml = rowHtmlOpen;
    chunk.forEach(function (col) {
        rowHtml += '<div class = "col col-4">' + col + '</div>'
    });
    rowHtml += rowHtmlClose;
    itemWrapper.append(rowHtml);
});

.row { margin: 10px 0; background: #ffe; }
.row > * { display: inline-block; margin: 0 10px; }

<script src = "https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class = "wrapper"></div>

var list = ["company1", "company2", "company3",
            "company4", "company5", "company6",
            "company7"];

var itemWrapper = document.querySelector('.wrapper');
var itemColumn = itemWrapper.querySelector('.col');
var output = '';

itemColumn.parentNode.removeChild(itemColumn);

list.forEach(function(company, index){
  if (index % 3 === 0) output += '<div class = "row">';
  
  itemColumn.innerText = company;
  output += itemColumn.outerHTML;
  
  if (++index % 3 === 0 || index === list.length) output += '</div>';
});

itemWrapper.innerHTML = output;

<div class = "wrapper">
    <div class = "row">
        <div class = "col col-4">x</div>
        <div class = "col col-4">c</div>
        <div class = "col col-4">v</div>
    </div>
</div>