Error codes in TypeScript

The numbers in parentheses after TypeScript errors, such as (18013), are error codes that uniquely identify the specific type of error reported by the TypeScript compiler. Each error code corresponds to a particular error scenario and helps in diagnosing and resolving issues more efficiently.

Purpose: These error codes provide a quick reference to the nature of the error. Developers can use these codes to look up detailed explanations and suggested fixes in the TypeScript documentation or other resources.
Error Code Ranges: TypeScript categorizes its error codes to help identify the type of error:
- 1xxx for syntactic errors
- 2xxx for semantic errors
- 4xxx for declaration emit errors
- 5xxx for compiler options errors
- 6xxx for command line errors
- 7xxx for type errors
Documentation and Tools: You can find explanations for these error codes in the TypeScript GitHub repository or through tools like the Pretty TypeScript Errors VS Code extension, which translates these codes directly in the IDE for better productivity [1].

Error Messages:

TypeScript error messages are designed to be informative and actionable. They often include suggestions on how to fix the issue, such as adding missing semicolons, correcting type mismatches, or providing explicit type annotations.

Common TypeScript Error Codes and their meanings:

TS1005: ';' expected: This error occurs when a semicolon is missing at the end of a statement.
TS1006: Identifier expected: This error occurs when an identifier is expected but not found.
TS1220: Element implicitly has an 'any' type because expression of type 'x' can't be used to index type 'y': This error occurs when TypeScript cannot determine the type of an object property.
TS1522: Variable 'x' is used before being assigned: This error occurs when a variable is used before it is assigned a value.
TS2300: Duplicate identifier 'x': This error occurs when a variable or type identifier is declared more than once.
TS2339: Property 'x' does not exist on type 'y': This error occurs when a property is accessed on a type that does not have that property.
TS2345: Argument of type 'x' is not assignable to parameter of type 'y': This error indicates a type mismatch between the argument and parameter types.
TS2532: Object is possibly 'undefined': This error occurs when TypeScript detects a potential undefined value in the code.
TS3145: Argument of type 'x' is not assignable to parameter of type 'y': This error occurs when a function argument does not match the expected parameter type.
TS3211: No value exists in scope for the shorthand property 'x': This error occurs when a shorthand property is used without a corresponding value.
TS3522: Type 'x' is not assignable to type 'y': This error occurs when a type is not compatible with another type.
TS3763: Overload signature is not compatible with function implementation: This error occurs when an overload signature does not match the function implementation.
TS4023: Exported variable 'x' has or is using private name 'y': This error occurs when an exported variable uses a private
TS4222: Property 'x' is missing in type 'y' but required in type 'z': This error occurs when a property is missing in a type that is expected to have that property.
TS4409: Cannot invoke an object which is possibly 'undefined': This error occurs when TypeScript detects a potential undefined value in the code.
TS4963: Parameter 'x' implicitly has an 'any' type: This error indicates that TypeScript could not infer the type of a parameter.
TS5155: Cannot find module 'x': This error occurs when TypeScript cannot find the specified module.
TS5216: Cannot assign to 'x' because it is a read-only property: This error occurs when an attempt is made to assign a value to a read-only property.
TS5403: Cannot find namespace 'x': This error occurs when TypeScript cannot find the specified namespace.
TS5619: Duplicate identifier 'x': This error occurs when a variable or type identifier is declared more than once.
TS6138: Property 'x' is declared but its value is never read: This error indicates that a property is declared but never used in the code.
TS6200: Unknown compiler option 'x': This error occurs when an unknown compiler option is specified in the TypeScript configuration.
TS6729: Cannot redeclare block-scoped variable 'x': This error occurs when a variable is declared more than once in the same block scope.
TS6883: Cannot find global value 'x': This error occurs when TypeScript cannot find the specified global value.
TS7006: Parameter 'x' implicitly has an 'any' type: This error indicates that TypeScript could not infer the type of a parameter.
TS7023: Element implicitly has an 'any' type because expression of type 'x' can't be used to index type 'y': This error occurs when TypeScript cannot determine the type of an object property.
TS7034: Variable 'x' implicitly has an 'any' type: This error indicates that TypeScript could not infer the type of a variable.
TS7035: Variable 'x' implicitly has type 'any' in some locations where its type cannot be determined: This error indicates that TypeScript could not infer the type of a variable in certain locations.

function calculateSum(a: number, b: number): number {
  if (a > 0 && b > 0) {
    return a + b;
  }
  // No return statement here
}

These error codes are part of TypeScript’s design to make the development process smoother by providing clear, actionable feedback on what might be wrong in the code, and how it can potentially be fixed.

Error codes in TypeScript

Error Messages:

Common TypeScript Error Codes and their meanings:

Citations: