README.md

18048 - '{0}' is possibly 'undefined'

🔍 Regex Patterns

regexFind: /([a-zA-Z_$][a-zA-Z0-9_$]*)\.(length|toUpperCase|trim|\w+)/
regexReplace: $1?.$2

💡 Suggestion

Add undefined check or use optional chaining to handle the possibility of undefined values. Use nullish coalescing operator (??) or optional chaining (?.) for safe property access.

📝 Examples

Example 1: Property access on possibly undefined value

function processValue(value?: string) {
+  if (value === undefined) {
+    return
+  }
  console.log(value.length)
  const upper = value.toUpperCase()
  return value.trim()
}

Explanation: Add undefined check before accessing properties

Example 2: Using optional chaining

-  const result = data.trim()
+  const result = data?.trim() ?? ''

Explanation: Use optional chaining and nullish coalescing

🖼️ Visual Output

Command

npx tsc ./docs/18048/index.ts --noEmit --pretty --strict

Result

docs/18048/index.ts:6:15 - error TS18048: 'value' is possibly 'undefined'.

6   console.log(value.length)
                ~~~~~

docs/18048/index.ts:9:17 - error TS18048: 'value' is possibly 'undefined'.

9   const upper = value.toUpperCase()
                  ~~~~~

docs/18048/index.ts:12:10 - error TS18048: 'value' is possibly 'undefined'.

12   return value.trim()
          ~~~~~

OR (without --pretty flag):

docs/18048/index.ts(6,15): error TS18048: 'value' is possibly 'undefined'.
docs/18048/index.ts(9,17): error TS18048: 'value' is possibly 'undefined'.
docs/18048/index.ts(12,10): error TS18048: 'value' is possibly 'undefined'.