Cross highilight google apps script

crosshighlightappscript.txt

/**
 * OPTIMIZED Cross-Highlighting - No Lag Version
 * Only highlights cells within your actual data range
 */

function onSelectionChange(e) {
  var ss = e.source;
  var sheet = ss.getActiveSheet();
  var activeCell = ss.getActiveRange();
  
  // Only work with single cell selections
  if (activeCell.getNumRows() > 1 || activeCell.getNumColumns() > 1) {
    return;
  }
  
  // Get the actual data range instead of max rows/columns
  var dataRange = sheet.getDataRange();
  var lastRow = dataRange.getLastRow();
  var lastCol = dataRange.getLastColumn();
  
  // Add some padding (optional - adds 5 extra rows/cols beyond data)
  lastRow = Math.min(lastRow + 5, sheet.getMaxRows());
  lastCol = Math.min(lastCol + 5, sheet.getMaxColumns());
  
  // Clear previous highlights from the data range only
  sheet.getRange(1, 1, lastRow, lastCol).setBackground(null);
  
  var activeRow = activeCell.getRow();
  var activeCol = activeCell.getColumn();
  
  // Highlight row (only up to last column with data)
  if (activeRow <= lastRow) {
    sheet.getRange(activeRow, 1, 1, lastCol).setBackground("lightyellow");
  }
  
  // Highlight column (only up to last row with data)
  if (activeCol <= lastCol) {
    sheet.getRange(1, activeCol, lastRow, 1).setBackground("lightyellow");
  }
  
  // Highlight the active cell
  activeCell.setBackground("yellow");
}