Can I make a CSS grid with dynamic number of rows or columns?

What I wanna do is to make a CSS grid with a dynamic number of cells. For the sake of simplicity, let's assume there will always be four cells per row. Can I specify a grid with such a dynamic number of rows?

To make it easier, here's the Flexbox implementation:

const COLORS = [
  '#FE9',
  '#9AF',
  '#F9A',
  "#AFA",
  "#FA7"
];

function addItem(container, template) {
  let color = COLORS[_.random(COLORS.length - 1)];
  let num = _.random(10000);
  
  container.append(Mustache.render(template, { color, num }));
}

$(() => {
  const tmpl = $('#item_template').html()
  const container = $('#app');
  
  for(let i=0; i<5; i++) { addItem(container, tmpl); }
  
  $('#add_el').click(() => {
    addItem(container, tmpl);
  })
  
  container.on('click', '.del_el', (e) => {
    $(e.target).closest('.item').remove();
  });
});

.container {
  width: 100%;
  display: flex;
  flex-flow: row wrap;
  justify-content: flex-start;
}
.container .item {
  flex: 0 0 calc(25% - 1em);
  min-height: 120px;
  margin: 0.25em 0.5em;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/mustache.js/2.3.0/mustache.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="app" class="container">
</div>

<button id="add_el">Add element</button>

<template id="item_template">
  <div class="item" style="background: {{color}}">
    <p>{{ num }}</p>
    <p>
      <button class="del_el">Delete</button>
    </p>
  </div>
</template>

P.S. Apparently, I wasn't clear enough the first time... I want to recreate this effect using the latest CSS Grid Layout.

Okay, after reading the MDN reference, I found the answer! The key to dynamic rows (or columns) is the repeat property.

const COLORS = [
  '#FE9',
  '#9AF',
  '#F9A',
  "#AFA",
  "#FA7"
];

function addItem(container, template) {
  let color = COLORS[_.random(COLORS.length - 1)];
  let num = _.random(10000);
  
  container.append(Mustache.render(template, { color, num }));
}

$(() => {
  const tmpl = $('#item_template').html()
  const container = $('#app');
  
  for(let i=0; i<5; i++) { addItem(container, tmpl); }
  
  $('#add_el').click(() => {
    addItem(container, tmpl);
  })
  
  container.on('click', '.del_el', (e) => {
    $(e.target).closest('.item').remove();
  });
});

.container {
  width: 100%;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: repeat(auto-fill, 120px);
  grid-row-gap: .5em;
  grid-column-gap: 1em;
}

.container .item {
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/mustache.js/2.3.0/mustache.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="app" class="container">
</div>

<button id="add_el">Add element</button>

<template id="item_template">
  <div class="item" style="background: {{color}}">
    <p>{{ num }}</p>
    <p>
      <button class="del_el">Delete</button>
    </p>
  </div>
</template>

P.S. Or you can use grid-auto-rows in my particular example.

Simply use below code to generate grid columns automatically

.container {
  display: grid;
  grid-auto-flow: column;
}

For those landing here looking for a way to have a sort of dynamic table, with items wrapping to new rows, and still being aligned across rows, a pretty good solution is to use flex with flex-wrap and flex: 1 for all elements:

.container {
  width: 100%;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
}

.container .item {
  flex: 1;
}

Something like this?

$(document).ready(function() {
 //Prepare Element selectors
  var cssElem = $("#Dynam"), rowElem = $("#rows"), columnElem = $("#columns"), appElem = $("#app");
  var noItems = $(".item").length,defaultColumns = 4;
    
  //Init default state
  cssElem.html(".container .item {flex: 0 0 calc(" + (100 / defaultColumns) + "% - 1em);}");
  columnElem.val(defaultColumns);
  rowElem.val(Math.ceil(noItems / columnElem.val()));

  //Add listeners to change
  appElem.on("DOMSubtreeModified", function() {
    noItems = $(".item").length;
    rowElem.val(Math.ceil(noItems / columnElem.val()));
  });
  columnElem.on("change", function() {
    rowElem.val(Math.ceil(noItems / columnElem.val()));
    cssElem.html(".container .item {flex: 0 0 calc(" + (100 / columnElem.val()) + "% - 1em);}");
  });
  rowElem.on("change", function() {
    columnElem.val(Math.ceil(noItems / rowElem.val()));
    cssElem.html(".container .item {flex: 0 0 calc(" + (100 / columnElem.val()) + "% - 1em);}");
  });
});

const COLORS = ['#FE9', '#9AF', '#F9A', "#AFA", "#FA7"];

function addItem(container, template) {
  let color = COLORS[_.random(COLORS.length - 1)];
  let num = _.random(10000);

  container.append(Mustache.render(template, {
    color,
    num
  }));
}

$(() => {
  const tmpl = $('#item_template').html()
  const container = $('#app');

  for (let i = 0; i < 5; i++) {
    addItem(container, tmpl);
  }

  $('#add_el').click(() => {
    addItem(container, tmpl);
  })

  container.on('click', '.del_el', (e) => {
    $(e.target).closest('.item').remove();
  });
});

.container {
  width: 100%;
  display: flex;
  flex-flow: row wrap;
  justify-content: flex-start;
}

.container .item {
  min-height: 120px;
  margin: 0.25em 0.5em;
  overflow: hidden;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/mustache.js/2.3.0/mustache.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<style id="Dynam"></style>
<button id="add_el">Add element</button> rows:
<input id="rows" /> columns:<input id="columns" />

<div id="app" class="container">
</div>

<template id="item_template">
  <div class="item" style="background: {{color}}">
    <p>{{ num }}</p>
    <p>
      <button class="del_el">Delete</button>
    </p>
  </div>
</template>

You don't need to use repeat. Instead you can just set a variable --grid-template-columns from your javascript code.

rootEl.style.setProperty('--grid-template-columns' theGridTemplateColumnsValue)

theGridTemplateColumnsValue is a string that can also contains other css variables. This way you can have a dynamic number of columns per row.