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index.ts
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README.md

18049 - '{0}' is possibly 'null' or 'undefined'

🔍 Regex Patterns

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

💡 Suggestion

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

📝 Examples

Example 1: Property access on possibly null/undefined value

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

Explanation: Add null/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/18049/index.ts --noEmit --pretty --strict

Result

docs/18049/index.ts:2:15 - error TS18049: 'value' is possibly 'null' or 'undefined'.

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

docs/18049/index.ts:3:17 - error TS18049: 'value' is possibly 'null' or 'undefined'.

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

docs/18049/index.ts:4:10 - error TS18049: 'value' is possibly 'null' or 'undefined'.

4   return value.trim()
         ~~~~~

OR (without --pretty flag):

docs/18049/index.ts(2,15): error TS18049: 'value' is possibly 'null' or 'undefined'.
docs/18049/index.ts(3,17): error TS18049: 'value' is possibly 'null' or 'undefined'.
docs/18049/index.ts(4,10): error TS18049: 'value' is possibly 'null' or 'undefined'.