Javascript-Custom Errors

Custom errors in JavaScript are 8 types of error objects. which are raised in a try or catch expression depending on the error type. They are:

• Error
• EvalError
• RangeError
• ReferenceError
• SyntaxError
• TypeError
• URIError
• I analyzed them

Error:

This is a generic error. It’s the one all the other error objects inherit from.

It contains 2 properties:

message: Human-readable message that should explain what error happened.

name: Type of error occurred (the value of the particular error object name(TypeError / SyntaxError)).

EvalError:

It was used to specify that the global function eval() was used incorrectly and in a way incompatible with its definition.

RangeError:

A RangeError will fire and when a numeric value is not in its range of allowed values.

set an array length to a negative value:

[].length = -1 //RangeError: Invalid array length

set it to a number higher than 4294967295:

[].length = 4294967295 //4294967295
[].length = 4294967296 //RangeError: Invalid array length

most common range errors:

RangeError: Not a valid code point.

RangeError: invalid array length.

RangeError: invalid date.

RangeError: precision is out of range.

RangeError: radix must be an integer.

RangeError: repeat count must be less than infinity.

RangeError: repeat count must be non-negative.

ReferenceError:

It is indicated that an invalid reference value has been detected. A JavaScript programming language is trying to read a variable that does not exist.

dog //ReferenceError: dog is not defined
dog = 2 //ReferenceError: dog is not defined

most common reference errors:

ReferenceError: “x” is not defined.

ReferenceError: assignment to undeclared variable “x”.

ReferenceError: can’t access lexical declaration ‘X’ before initialization.

ReferenceError: deprecated caller or argument usage.

ReferenceError: invalid assignment left-hand side.

ReferenceError: reference to undefined property “x”.

SyntaxError:

It is raised when a syntax error is found in a program.

function statement without name:

function() {
 return 'Hi!'
}

//SyntaxError: function statement requires a name

comma after an object property:

const dog = {
 name: 'Roger'
 age: 5
}

//SyntaxError: missing } after property list

common syntax errors:

SyntaxError: “0”-prefixed octal literals and octal escape seq. are deprecated

SyntaxError: “use strict” not allowed in function(non-simple parameters).

SyntaxError: “x” is a reserved identifier.

SyntaxError: JSON.parse: bad parsing.

SyntaxError: Malformed formal parameter.

SyntaxError: Unexpected token.

SyntaxError:  //@ to indicate source URL pragmas is deprecated. Use //# instead.

SyntaxError: illegal character.

SyntaxError: invalid regular expression flag “x”.

SyntaxError: missing ) after argument list.

SyntaxError: missing ) after condition.

SyntaxError: missing : after property id.

SyntaxError: missing ; before statement.

SyntaxError: missing = in const declaration.

SyntaxError: missing \] after element list.

SyntaxError: missing formal parameter.

SyntaxError: missing name after . operator.

SyntaxError: missing variable name.

SyntaxError: missing } after function body.

SyntaxError: missing } after property list.

SyntaxError: redeclaration of formal parameter “x”.

SyntaxError: return not in function.

TypeError:

It happens when a value has a type that is different than the one expected.

trying to invoke a number:

1() //TypeError: 1 is not a function

common type errors:

TypeError: “x” has no properties

TypeError: “x” is (not) “y”

TypeError: “x” is not a constructor

TypeError: “x” is not a function

TypeError: “x” is not a non-null object

TypeError: “x” is read-only

TypeError: ‘x’ is not iterable

TypeError: More arguments needed

TypeError: invalid arguments

TypeError: cyclic object value

URIError:

It is raised when returning one of the global function() that work with URIs:

• decodeURI()
• decodeURIComponent()
• encodeURI()
• encodeURIComponent()

and passing an invalid URI.