Code Inspections in JavaScript
In JavaScript, ReSharper 2021.1 provides two kinds of code inspections: 4 inspections that detect errors such as broken syntax, unresolved symbols, compiler errors, and so on (you cannot configure or disable any of these inspections), and 113 proprietary code inspections, any of which you can disable or change its severity level.
These code inspections help you detect code issues in design time in all open files, and additionally they allow you to find code issues in specific scope.
Configurable JavaScript inspections are listed below, grouped by their categories.
Common Practices and Code Improvements (3 inspections)
This category groups inspections that hunt for medium severity issues that mainly affect code readability.| Inspection ID EditorConfig property | Default severity |
|---|---|
Join local variable declaration and assignment JoinDeclarationAndInitializerJs resharper_join_declaration_and_initializer_js_highlighting | Suggestion |
Statement termination doesn't match code style StatementTermination resharper_statement_termination_highlighting | Warning |
Use of future reserved word UsingOfReservedWord resharper_using_of_reserved_word_highlighting | Warning |
Constraints Violations (1 inspection)
This category includes code inspections, mostly with the warning severity level, which detect violations related to symbol attributes, including ReSharper's code annotations, and other similar issues.| Inspection ID EditorConfig property | Default severity |
|---|---|
Inconsistent Naming InconsistentNaming resharper_inconsistent_naming_highlighting | Warning |
Language Usage Opportunities (9 inspections)
This category includes code inspections, mostly with the suggestion severity level, which notify you when more advanced language constructs can be used. These inspections detect syntax of outdated language versions and suggest using features from more modern language versions. For most of the supported languages, language version can be detected automatically or set manually.| Inspection ID EditorConfig property | Default severity |
|---|---|
A series of undefined-checks for properties can be replaced with destructuring ReplaceUndefinedCheckingSeriesWithObjectDestructuring resharper_replace_undefined_checking_series_with_object_destructuring_highlighting | Hint |
Intermediate local variable is redundant and can be safely inlined RedundantIntermediateVariable resharper_redundant_intermediate_variable_highlighting | Hint |
Intermediate local variable is redundant because it can be replaced with a destructuring swap expression ReplaceWithDestructuringSwap resharper_replace_with_destructuring_swap_highlighting | Hint |
Local variable can be safely moved to inner block VariableCanBeMovedToInnerBlock resharper_variable_can_be_moved_to_inner_block_highlighting | Hint |
String concatenation can be converted to a template string StringConcatenationToTemplateString resharper_string_concatenation_to_template_string_highlighting | Hint |
Subsequent indexers can be replaced by a destructuring declaration or assignment ReplaceIndicingWithArrayDestructuring resharper_replace_indicing_with_array_destructuring_highlighting | Hint |
Subsequent indexers in object literal fields can be simplified with destructuring ReplaceIndicingWithShortHandPropertiesAfterDestructuring resharper_replace_indicing_with_short_hand_properties_after_destructuring_highlighting | Hint |
'var' variable can be made 'let' variable VariableCanBeMadeLet resharper_variable_can_be_made_let_highlighting | Hint |
Variable can be made constant VariableCanBeMadeConst resharper_variable_can_be_made_const_highlighting | Hint |
Potential Code Quality Issues (68 inspections)
This category includes inspections that detect critical issues (code smells), mostly with Error or Warning level. This category also includes inspections that ensure localization assistance.| Inspection ID EditorConfig property | Default severity |
|---|---|
'?:' expression has identical true and false branches ConditionalTernaryEqualBranch resharper_conditional_ternary_equal_branch_highlighting | Warning |
A trailing element of an array is elided ElidedTrailingElement resharper_elided_trailing_element_highlighting | Warning |
Assignment to a variable inside a conditional statement AssignmentInConditionExpression resharper_assignment_in_condition_expression_highlighting | Warning |
Assignment to an implicitly declared global variable AssignToImplicitGlobalInFunctionScope resharper_assign_to_implicit_global_in_function_scope_highlighting | Warning |
Assignment to constant AssignToConstant resharper_assign_to_constant_highlighting | Error |
Cannot resolve symbol NotResolved resharper_not_resolved_highlighting | Warning |
Closure on a variable modified in loop of outer scope ClosureOnModifiedVariable resharper_closure_on_modified_variable_highlighting | Warning |
Comma is expected in object literal ObjectLiteralsAreNotCommaFree resharper_object_literals_are_not_comma_free_highlighting | Error |
Comma is not valid here CommaNotValidHere resharper_comma_not_valid_here_highlighting | Error |
Comparison of 'typeof' expression with incorrect value IncorrectOperandInTypeOfComparison resharper_incorrect_operand_in_type_of_comparison_highlighting | Warning |
Condition is always constant ConditionIsAlwaysConst resharper_condition_is_always_const_highlighting | Warning |
Constructor call is not used or possibly used for side-effects ConstructorCallNotUsed resharper_constructor_call_not_used_highlighting | Warning |
Declaration hides another declaration from an outer scope DeclarationHides resharper_declaration_hides_highlighting | Hint |
Duplicate property declaration DuplicatingPropertyDeclaration resharper_duplicating_property_declaration_highlighting | Warning |
Duplicate switch label DuplicatingSwitchLabel resharper_duplicating_switch_label_highlighting | Warning |
ECMAScript 2015 feature usage when in ES 5 or lower Es6Feature resharper_es6_feature_highlighting | Error |
ECMAScript 2016 feature usage when in ES 2015 or lower Es7Feature resharper_es7_feature_highlighting | Error |
Error in XML doc comment reference ErrorInXmlDocReference resharper_error_in_xml_doc_reference_highlighting | Error |
Experimental feature usage when language level set to stable ExperimentalFeature resharper_experimental_feature_highlighting | Error |
Expression is always constant ExpressionIsAlwaysConst resharper_expression_is_always_const_highlighting | Warning |
Expression is expected after 'throw' statement ThrowMustBeFollowedByExpression resharper_throw_must_be_followed_by_expression_highlighting | Error |
Extending prototype of native object NativeTypePrototypeExtending resharper_native_type_prototype_extending_highlighting | Warning |
Heuristically unreachable code HeuristicallyUnreachableCode resharper_heuristically_unreachable_code_highlighting | Warning |
Illegal syntax in XML code comment XmlDocCommentSyntaxProblem resharper_xml_doc_comment_syntax_problem_highlighting | Warning |
'import' keyword is not allowed here. ImportKeywordNotWithInvocation resharper_import_keyword_not_with_invocation_highlighting | Error |
Inconsistent function returns InconsistentFunctionReturns resharper_inconsistent_function_returns_highlighting | Warning |
Invalid JSON syntax InvalidJsonSyntax resharper_invalid_json_syntax_highlighting | Error |
Invocation of non-function expression InvocationOfNonFunction resharper_invocation_of_non_function_highlighting | Warning |
Invoked expression is not a function value InvokedExpressionMaybeNonFunction resharper_invoked_expression_maybe_non_function_highlighting | Warning |
JSON validation failed JsonValidationFailed resharper_json_validation_failed_highlighting | Error |
Lexical declaration can only be declared inside a block. LexicalDeclarationNeedsBlock resharper_lexical_declaration_needs_block_highlighting | Error |
Local function is redefined later LocalFunctionRedefinedLater resharper_local_function_redefined_later_highlighting | Warning |
L-value expected error LValueIsExpected resharper_l_value_is_expected_highlighting | Error |
Misuse of 'this' qualifier in inner function MisuseOfOwnerFunctionThis resharper_misuse_of_owner_function_this_highlighting | Warning |
Multiple declarations in 'for in' error MultipleDeclarationsInForeach resharper_multiple_declarations_in_foreach_highlighting | Error |
Non-assigned constant NonAssignedConstant resharper_non_assigned_constant_highlighting | Error |
Non-parenthesized object destructuring assignment cannot be used in an expression statement ObjectDestructuringWithoutParentheses resharper_object_destructuring_without_parentheses_highlighting | Error |
Not all code paths return a value NotAllPathsReturnValue resharper_not_all_paths_return_value_highlighting | Warning |
Object property declaration is expected EmptyObjectPropertyDeclaration resharper_empty_object_property_declaration_highlighting | Error |
Overwriting prototype of native object NativeTypePrototypeOverwriting resharper_native_type_prototype_overwriting_highlighting | Warning |
Parameter name 'arguments' clashes with pre-defined JS function-scope variable FunctionParameterNamedArguments resharper_function_parameter_named_arguments_highlighting | Warning |
Parameter value is not used ParameterValueIsNotUsed resharper_parameter_value_is_not_used_highlighting | Warning |
Path for reference comment not found JsPathNotFound resharper_js_path_not_found_highlighting | Error |
Possible mistake: ambiguous lambda block and object literal SuspiciousLambdaBlock resharper_suspicious_lambda_block_highlighting | Warning |
Property getter cannot have parameters PropertyGetterCannotHaveParameters resharper_property_getter_cannot_have_parameters_highlighting | Error |
Property setter must have a single parameter PropertySetterMustHaveSingleParameter resharper_property_setter_must_have_single_parameter_highlighting | Error |
Qualifier can be 'null' or 'undefined' QualifiedExpressionMaybeNull resharper_qualified_expression_maybe_null_highlighting | Warning |
Qualifier is 'null' or 'undefined' QualifiedExpressionIsNull resharper_qualified_expression_is_null_highlighting | Warning |
Redeclaration of let/const BlockScopeRedeclaration resharper_block_scope_redeclaration_highlighting | Error |
Return statement with a value in the global scope ReturnFromGlobalScopetWithValue resharper_return_from_global_scopet_with_value_highlighting | Warning |
Similar expressions comparison SimilarExpressionsComparison resharper_similar_expressions_comparison_highlighting | Warning |
Statement is possibly incorrectly broken by a newline PossiblyIncorrectlyBrokenStatement resharper_possibly_incorrectly_broken_statement_highlighting | Warning |
'super' must be called before accessing 'this' in the constructor of a derived class. SuperCallProhibitsThis resharper_super_call_prohibits_this_highlighting | Error |
Suspicious expression statement WrongExpressionStatement resharper_wrong_expression_statement_highlighting | Warning |
There is no .hasOwnProperty() check in a body of 'for in' loop. This will cause an enumeration of prototype properties MissingHasOwnPropertyInForeach resharper_missing_has_own_property_in_foreach_highlighting | Warning |
Trailing redundant comma in object properties list may be error UnsafeCommaInObjectPropertiesList resharper_unsafe_comma_in_object_properties_list_highlighting | Warning |
Triple-slash directives are only valid at the top of the file IncorrectTripleSlashLocation resharper_incorrect_triple_slash_location_highlighting | Warning |
Usage of possibly unassigned local variable UsageOfPossiblyUnassignedValue resharper_usage_of_possibly_unassigned_value_highlighting | Warning |
Usage of unassigned local variable UsageOfDefinitelyUnassignedValue resharper_usage_of_definitely_unassigned_value_highlighting | Warning |
Use 'break' or 'continue' outside of loop body JumpMustBeInLoop resharper_jump_must_be_in_loop_highlighting | Warning |
Use of expression after break or continue LabelOrSemicolonExpected resharper_label_or_semicolon_expected_highlighting | Error |
Use of implicitly declared global variable UseOfImplicitGlobalInFunctionScope resharper_use_of_implicit_global_in_function_scope_highlighting | Warning |
Use of possibly unassigned property or global variable PossiblyUnassignedProperty resharper_possibly_unassigned_property_highlighting | Hint |
Use of 'this' in global context ThisInGlobalContext resharper_this_in_global_context_highlighting | Warning |
Using of 'arguments.caller' and 'arguments.callee' CallerCalleeUsing resharper_caller_callee_using_highlighting | Warning |
Using of coerced equality (using of coerced equality operator with 'null' or 'undefined') CoercedEqualsUsingWithNullUndefined resharper_coerced_equals_using_with_null_undefined_highlighting | Disabled |
Using of coerced equality (using of coerced equality operator) CoercedEqualsUsing resharper_coerced_equals_using_highlighting | Warning |
Variable is used before it is declared VariableUsedBeforeDeclared resharper_variable_used_before_declared_highlighting | Warning |
Redundancies in Code (4 inspections)
Code inspections in this category look for redundancies and dead code, which affect code readability and style, and could be safely removed. Some code redundancies cannot be fixed automatically, and quick-fixes for them are performed in the interactive mode, requiring the user input. But the majority of the redundancies can be fixed without user interaction, using either fix in scope or code cleanup.| Inspection ID EditorConfig property | Default severity |
|---|---|
Assigned value is never used AssignedValueIsNeverUsed resharper_assigned_value_is_never_used_highlighting | Warning |
Redundant block RedundantBlock resharper_redundant_block_highlighting | Warning |
Redundant empty finally block RedundantEmptyFinallyBlock resharper_redundant_empty_finally_block_highlighting | Warning |
Unreachable code JsUnreachableCode resharper_js_unreachable_code_highlighting | Warning |
Redundancies in Symbol Declarations (11 inspections)
This category includes code inspections, mostly with the warning severity level, which detect empty and unused symbol declarations.| Inspection ID EditorConfig property | Default severity |
|---|---|
Assignment of a local variable to itself is redundant SameVariableAssignment resharper_same_variable_assignment_highlighting | Warning |
Duplicate local declaration DuplicatingLocalDeclaration resharper_duplicating_local_declaration_highlighting | Warning |
Redundant 'else' block RedundantElseBlock resharper_redundant_else_block_highlighting | Warning |
Redundant local class name RedundantLocalClassName resharper_redundant_local_class_name_highlighting | Hint |
Redundant local function name RedundantLocalFunctionName resharper_redundant_local_function_name_highlighting | Hint |
Type is never used (non-private accessibility) UnusedType.Global resharper_unused_type_global_highlighting | Suggestion |
Type member is never used (non-private accessibility) UnusedMember.Global resharper_unused_member_global_highlighting | Suggestion |
Unused local variable / function / class UnusedLocals resharper_unused_locals_highlighting | Warning |
Unused parameter UnusedParameter resharper_unused_parameter_highlighting | Warning |
Unused parameter of inherited member UnusedInheritedParameter resharper_unused_inherited_parameter_highlighting | Hint |
Unused property or function UnusedProperty resharper_unused_property_highlighting | Warning |
Spelling issues (3 inspections)
These inspections detect typos in various contexts.| Inspection ID EditorConfig property | Default severity |
|---|---|
Typo in comment CommentTypo resharper_comment_typo_highlighting | Suggestion |
Typo in identifier IdentifierTypo resharper_identifier_typo_highlighting | Suggestion |
Typo in string literal StringLiteralTypo resharper_string_literal_typo_highlighting | Suggestion |
Strict mode violations (9 inspections)
| Inspection ID EditorConfig property | Default severity |
|---|---|
Calling 'delete' on non-qualified identifier in 'strict mode' DeletingNonQualifiedReference resharper_deleting_non_qualified_reference_highlighting | Error |
Duplicate parameter declaration in 'strict mode' DuplicatingParameterDeclarationError resharper_duplicating_parameter_declaration_error_highlighting | Error |
Duplicate property declaration in 'strict mode' DuplicatingPropertyDeclarationError resharper_duplicating_property_declaration_error_highlighting | Error |
Octal literals and escape sequences using in 'strict mode' OctalLiteralsNotAllowedError resharper_octal_literals_not_allowed_error_highlighting | Error |
Using of 'arguments.caller' and 'arguments.callee' in 'strict mode' CallerCalleeUsingError resharper_caller_callee_using_error_highlighting | Error |
Using of 'eval'/'arguments' name in 'strict mode' EvalArgumentsNameError resharper_eval_arguments_name_error_highlighting | Error |
Using of future reserved keywords in 'strict mode' UsingOfReservedWordError resharper_using_of_reserved_word_error_highlighting | Error |
Using of undeclared global variable UndeclaredGlobalVariableUsing resharper_undeclared_global_variable_using_highlighting | Warning |
Using of 'with' statements in 'strict mode' WithStatementUsingError resharper_with_statement_using_error_highlighting | Error |
Syntax Style (5 inspections)
Inspections in this category detect violations of code syntax styles. In contrast to most of other code inspections, these inspections can either detect the same code construct as a code issue or not depending on the corresponding code style rule configured on the page of ReSharper options(Alt+R, O). You can also fix issues that these inspection detect using code cleanup.| Inspection ID EditorConfig property | Default severity |
|---|---|
Function is used before it is declared FunctionsUsedBeforeDeclared resharper_functions_used_before_declared_highlighting | Disabled |
Function is used outside of scope which it is declared FunctionUsedOutOfScope resharper_function_used_out_of_scope_highlighting | Warning |
Non-compliant quotes around string literal StringLiteralWrongQuotes resharper_string_literal_wrong_quotes_highlighting | Hint |
Variable is used in inner scope before it is declared VariableUsedInInnerScopeBeforeDeclared resharper_variable_used_in_inner_scope_before_declared_highlighting | Warning |
Variable is used outside of scope which it is declared VariableUsedOutOfScope resharper_variable_used_out_of_scope_highlighting | Warning |
Last modified: 12 July 2021