# Duplicate Rule

## Content

The duplicate rule checks for duplicate values.

![](https://gcdocumentsitekrblob.blob.core.windows.net/document-site-files/images/8d606653-16a0-474d-b9dc-e2b4d01c2446/images/duplicate.png)

The following code sample creates a duplicate rule.

```javascript
var style = new GC.Spread.Sheets.Style();
style.backColor = "yellow";
var ranges=[new GC.Spread.Sheets.Range(0,0,10,1)];
activeSheet.conditionalFormats.addDuplicateRule(style, ranges);
activeSheet.setValue(0, 0, 50);
activeSheet.setValue(1, 0, 50);
activeSheet.setValue(2, 0, 11);
activeSheet.setValue(3, 0, 5);
// OR
var style = new GC.Spread.Sheets.Style();
style.backColor = "yellow";
var rule = new GC.Spread.Sheets.ConditionalFormatting.NormalConditionRule();
rule.ruleType(GC.Spread.Sheets.ConditionalFormatting.RuleType.DuplicateRule);
rule.ranges([new GC.Spread.Sheets.Range(0,0,10,1)]);
rule.style(style);
activeSheet.conditionalFormats.addRule(rule);
activeSheet.setValue(0, 0, 50);
activeSheet.setValue(1, 0, 50);
activeSheet.setValue(2, 0, 11);
activeSheet.setValue(3, 0, 5);
```