1---
2title: Use Collapsed Constant for Unused Lines
3impact: HIGH
4tags: morphing, collapsed, structure
5---
6 
7## Use Collapsed Constant for Unused Lines
8 
9Unused lines must use the collapsed constant, not omission or null.
10 
11**Incorrect (null for unused):**
12 
13```ts
14const minusIcon = {
15  lines: [
16    { x1: 2, y1: 7, x2: 12, y2: 7 },
17    null,
18    null,
19  ],
20};
21```
22 
23**Correct (collapsed constant):**
24 
25```ts
26const minusIcon = {
27  lines: [
28    { x1: 2, y1: 7, x2: 12, y2: 7 },
29    collapsed,
30    collapsed,
31  ],
32};
33```
34