TypeScript Code

link - learn.microsoft.com/en-us/office/dev/add-ins/excel/excel-add-ins-conditional-formatting

Excel.run ( function (context) { 
   var _sheet = context.workbook.worksheets.getActiveWorksheet(); 
   var _range = _sheet.getRange("A1:E10"); 
   var _conditionalFormat = _range.conditionalFormats.add(Excel.ConditionalFormatType.custom); 

   _conditionalFormat.custom.format.fill.color = "yellow"; 
   _conditionalFormat.custom.rule.formula = "If((AND($E1>100,$E1<300)),TRUE)"; 

   //alternative syntax 
   _conditionalFormat.custom.rule.formula = {formula1: "=100", formula2="=300", operator:"Between"}; 
} 

This script applies green fill conditional formatting to the top 10% of values in the used range.

function main(workbook: ExcelScript.Workbook) { 
  let selectedSheet = workbook.getActiveWorksheet(); 
  let range = selectedSheet.getUsedRange(); 

  let conditionalFormat = range.addConditionalFormat(ExcelScript.ConditionalFormatType.topBottom) 
  conditionalFormat.getTopBottom().getFormat().getFill().setColor("green"); 
  conditionalFormat.getTopBottom().setRule({ 
    rank: 10, 
    type: ExcelScript.ConditionalTopBottomCriterionType.topPercent 
  }); 
}