EC
TS95018
TypeScriptERRORNotableConfigHIGH confidence

Add 'undefined' type to property 'X'

Production Risk

Build will fail; resolve before shipping.

What this means

A TypeScript diagnostic (TS95018): Add 'undefined' type to property 'X'. This diagnostic is emitted by the TypeScript compiler when add 'undefined' type to property 'X'.

Why it happens
  1. 1Incorrect TypeScript syntax or type usage
  2. 2Type mismatch between declared and actual value
How to reproduce

TypeScript compiler reports TS95018 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS95018
// Add 'undefined' type to property 'X'

expected output

error TS95018: Add 'undefined' type to property 'X'

Fix

Fix the tsconfig.json option

WHEN When a compiler option is invalid or missing

Fix the tsconfig.json option
// tsconfig.json
{
  "compilerOptions": {
    // Review and correct the flagged option
  }
}
// Run: npx tsc --showConfig to see effective config

Why this works

TypeScript validates tsconfig.json options; check the official tsconfig reference for valid values.

Sources
Official documentation ↗

TypeScript Compiler Diagnostics

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