---
source: crates/biome_js_analyze/tests/spec_tests.rs
expression: functionalChain.js
---
# Input
```jsx
function functionalChain(array) {
    return array
        .filter(Boolean)
        .flatMap(items => {              // nesting = 1
            if (items.length > 1) {      // +2
                return items;
            } else {                     // +1
                return [];
            }
        })
        .filterMap(item => (             // nesting = 1
            item > 0 ? 2 * item : null   // +2
        ));
}

```

# Diagnostics
```
functionalChain.js:4:24 lint/complexity/noExcessiveCognitiveComplexity ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! Excessive complexity detected.
  
    2 │     return array
    3 │         .filter(Boolean)
  > 4 │         .flatMap(items => {              // nesting = 1
      │                        ^^^
    5 │             if (items.length > 1) {      // +2
    6 │                 return items;
  
  i Please refactor this function to reduce its complexity score from 3 to the max allowed complexity 2.
  

```