// Adds a conditional format rule to a sheet that causes cells in range A1:B3 to turn red if
// they contain a number between 1 and 10.
var sheet = SpreadsheetApp.getActiveSheet();
var range = sheet.getRange("A1:B3");
var rule = SpreadsheetApp.newConditionalFormatRule()
.whenNumberBetween(1, 10)
.setBackground("#FF0000")
.setRanges([range])
.build();
var rules = sheet.getConditionalFormatRules();
rules.push(rule);
sheet.setConditionalFormatRules(rules);
Builder for conditional format rules.