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HTML Settings

Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

              <div id="container">
  <div class="item grey"></div>
  <div class="item purple"></div>  
  <div class="item orange"></div>
  <div class="item blue"></div>
              body {
  margin: 20px;

  display: grid;
  width: 100%;
  height: 350px;
  grid-template-columns: [full-start] 1fr 1fr [full-end];
  grid-template-rows: 100px 1fr 100px;
  grid-gap: 20px;

.purple {
  grid-row: span 2;

.blue {
  grid-column: span 2;
              const container = document.getElementById("container");
const inspector = document.createElement('div');

inspector.setAttribute('style', `
  position: absolute;
  height: ${container.offsetHeight}px;
  width: ${container.offsetWidth}px;
  top: ${container.offsetTop}px;
  left: ${container.offsetLeft}px;


// get the rows/columns/gaps
const styles = window.getComputedStyle(container);

const rows = styles.getPropertyValue("grid-template-rows");
const columns = styles.getPropertyValue("grid-template-columns");

const rowGap = styles.getPropertyValue("grid-row-gap");
const columnGap = styles.getPropertyValue("grid-column-gap");

// convert the rows and columns into a format we can work with
const columnData = parseGridTemplate(columns, columnGap);
const rowData = parseGridTemplate(rows, rowGap);

const extendLines = 20;

// render a line for each vertical grid line
columnData.forEach((item) => {
  const line = document.createElement('div');
  line.setAttribute('style', `
    background: black;
    position: absolute;
    height: ${container.offsetHeight + extendLines * 2}px;
    width: ${item.end - item.start + ( || 0)}px;
    left: ${item.start}px;
    top: ${-extendLines}px;

// render a line for each horizontal grid line
rowData.forEach((item) => {
  const line = document.createElement('div');
  line.setAttribute('style', `
    background: black;
    position: absolute;
    width: ${container.offsetWidth + extendLines * 2}px;
    height: ${item.end - item.start + ( || 0)}px;
    top: ${item.start}px;
    left: ${-extendLines}px;

  Converts a grid template string into an array of grid line objects
  Example input: "[full-start] 300px 300px [full-end]"
  Example outut:
    "start": -1,
    "end": 1,
    "name": "full-start"
    "start": 299,
    "end": 301,
    "name": null,
    "gap": 20
    "start": 619,
    "end": 621,
    "name": "full-end"
function parseGridTemplate(templateStr, gap = "0px") {
  const gapSize = parseFloat(gap.replace("px", ""));

  // splits at and space that isn't between two [ ] brackets
  const parsedArray = templateStr.split(/\s(?![^[]*])/);
  let lines = [];
  let currentPosition = 0;

  // add in any missing names as ""
  // "200px [center-start] 300px [center-end] 400px" becomes:
  // "'' 200px [center-start] 300px [center-end] 400px ''"

  let allItems = [];

  parsedArray.forEach((item, index) => {
    if (item.includes("px")) {
      // add a null name before it if missing
      if (!parsedArray[index - 1] || parsedArray[index - 1].includes("px")) {


  // handle last item
  if (parsedArray[parsedArray.length - 1].includes("px")) {

  allItems.forEach((item, index) => {
    if (item.includes("px")) {
      const trackSize = parseFloat(item.replace("px", ""));
      currentPosition += trackSize;
    } else {
      let newLine = {
        start: currentPosition - 1,
        end: currentPosition + 1,
        name: getName(item)
      // add gaps on just the inner lines
      // and count it for positioning
      if (index !== 0 && index !== allItems.length - 1 && gapSize !== 0) { = gapSize;
        currentPosition += gapSize;


  return lines;

function getName(item) {
  return item.includes("[") ? item.match(/\[(.*)\]/)[1].trim() : null;
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