EC
TS6699
TypeScriptERRORNotableConfigHIGH confidence

When type checking, take into account 'null' and 'undefined'.

Production Risk

Build will fail; resolve before shipping.

What this means

A compiler configuration error (TS6699): When type checking, take into account 'null' and 'undefined'.. This diagnostic is emitted by the TypeScript compiler when when type checking, take into account 'null' and 'undefined'..

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

TypeScript compiler reports TS6699 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS6699
// When type checking, take into account 'null' and 'undefined'.

expected output

error TS6699: When type checking, take into account 'null' and 'undefined'.

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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