Class AssertionError

Indicates the failure of an assertion. All errors thrown by the node:assert module will be instances of the AssertionError class.

Hierarchy

  • Error
    • AssertionError

Constructors

constructor

Properties

actual cause? code expected generatedMessage message name operator stack? stackTraceLimit

Methods

captureStackTrace prepareStackTrace

Constructors

constructor

  • new AssertionError(
        options?: {
            actual?: unknown;
            expected?: unknown;
            message?: string;
            operator?: string;
            stackStartFn?: Function;
        },
    ): assert.AssertionError

    Parameters

    • Optionaloptions: {
          actual?: unknown;
          expected?: unknown;
          message?: string;
          operator?: string;
          stackStartFn?: Function;
      }
      • Optionalactual?: unknown

        The actual property on the error instance.

      • Optionalexpected?: unknown

        The expected property on the error instance.

      • Optionalmessage?: string

        If provided, the error message is set to this value.

      • Optionaloperator?: string

        The operator property on the error instance.

      • OptionalstackStartFn?: Function

        If provided, the generated stack trace omits frames before this function.

    Returns assert.AssertionError

Properties

actual

actual: unknown

Set to the actual argument for methods such as ().

Optionalcause

cause?: unknown

code

code: "ERR_ASSERTION"

Value is always ERR_ASSERTION to show that the error is an assertion error.

expected

expected: unknown

Set to the expected argument for methods such as ().

generatedMessage

generatedMessage: boolean

Indicates if the message was auto-generated (true) or not.

message

message: string

name

name: string

operator

operator: string

Set to the passed in operator value.

Optionalstack

stack?: string

StaticstackTraceLimit

stackTraceLimit: number

The Error.stackTraceLimit property specifies the number of stack frames collected by a stack trace (whether generated by new Error().stack or Error.captureStackTrace(obj)).

The default value is 10 but may be set to any valid JavaScript number. Changes will affect any stack trace captured after the value has been changed.

If set to a non-number value, or set to a negative number, stack traces will not capture any frames.

Methods

StaticcaptureStackTrace

  • captureStackTrace(targetObject: object, constructorOpt?: Function): void

    Creates a .stack property on targetObject, which when accessed returns a string representing the location in the code at which Error.captureStackTrace() was called.

    const myObject = {};
    Error.captureStackTrace(myObject);
    myObject.stack;  // Similar to `new Error().stack`

    The first line of the trace will be prefixed with ${myObject.name}: ${myObject.message}.

    The optional constructorOpt argument accepts a function. If given, all frames above constructorOpt, including constructorOpt, will be omitted from the generated stack trace.

    The constructorOpt argument is useful for hiding implementation details of error generation from the user. For instance:

    function a() {
      b();
    }

    function b() {
      c();
    }

    function c() {
      // Create an error without stack trace to avoid calculating the stack trace twice.
      const { stackTraceLimit } = Error;
      Error.stackTraceLimit = 0;
      const error = new Error();
      Error.stackTraceLimit = stackTraceLimit;

      // Capture the stack trace above function b
      Error.captureStackTrace(error, b); // Neither function c, nor b is included in the stack trace
      throw error;
    }

    a();

    Parameters

    • targetObject: object
    • OptionalconstructorOpt: Function

    Returns void

StaticprepareStackTrace

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