EC
TS1060
TypeScriptERRORNotableSyntaxHIGH confidence

The first parameter of the 'then' method of a promise must be a callback.

Production Risk

Build will fail; resolve before shipping.

What this means

A syntax error (TS1060): The first parameter of the 'then' method of a promise must be a callback.. This diagnostic is emitted by the TypeScript compiler when the first parameter of the 'then' method of a promise must be a callback..

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

TypeScript compiler reports TS1060 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS1060
// The first parameter of the 'then' method of a promise must be a callback.

expected output

error TS1060: The first parameter of the 'then' method of a promise must be a callback.

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.

Sources
Official documentation ↗

TypeScript Compiler Diagnostics

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