EC
TS2358
TypeScriptERRORNotableTypeHIGH confidence

The left-hand side of an 'instanceof' expression must be of type 'any', an ob...

Production Risk

Build will fail; resolve before shipping.

What this means

A type-checking error (TS2358): The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.. This diagnostic is emitted by the TypeScript compiler when the left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter..

Why it happens
  1. 1Incorrect number or type of generic type arguments
How to reproduce

TypeScript compiler reports TS2358 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS2358
// The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.

expected output

error TS2358: The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.

Fix

Address the TypeScript diagnostic

WHEN When this error is reported by the compiler

Address the TypeScript diagnostic
// Run the TypeScript compiler for details:
npx tsc --noEmit
// Use the TypeScript playground to test your code:
// https://www.typescriptlang.org/play

Why this works

Review the full error message and location; the TypeScript handbook provides guidance on each error category.

What not to do

✕ Suppress with @ts-ignore instead of fixing the type

ts-ignore hides real type errors and makes refactoring unsafe.

Sources
Official documentation ↗

TypeScript Compiler Diagnostics

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