Showing 686 of 688 total issues
Missing radix parameter. Open
count = parseInt(count) + value;
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Require Radix Parameter (radix)
When using the parseInt()
function it is common to omit the second argument, the radix, and let the function try to determine from the first argument what type of number it is. By default, parseInt()
will autodetect decimal and hexadecimal (via 0x
prefix). Prior to ECMAScript 5, parseInt()
also autodetected octal literals, which caused problems because many developers assumed a leading 0
would be ignored.
This confusion led to the suggestion that you always use the radix parameter to parseInt()
to eliminate unintended consequences. So instead of doing this:
var num = parseInt("071"); // 57
Do this:
var num = parseInt("071", 10); // 71
ECMAScript 5 changed the behavior of parseInt()
so that it no longer autodetects octal literals and instead treats them as decimal literals. However, the differences between hexadecimal and decimal interpretation of the first parameter causes many developers to continue using the radix parameter to ensure the string is interpreted in the intended way.
On the other hand, if the code is targeting only ES5-compliant environments passing the radix 10
may be redundant. In such a case you might want to disallow using such a radix.
Rule Details
This rule is aimed at preventing the unintended conversion of a string to a number of a different base than intended or at preventing the redundant 10
radix if targeting modern environments only.
Options
There are two options for this rule:
-
"always"
enforces providing a radix (default) -
"as-needed"
disallows providing the10
radix
always
Examples of incorrect code for the default "always"
option:
/*eslint radix: "error"*/
var num = parseInt("071");
var num = parseInt(someValue);
var num = parseInt("071", "abc");
var num = parseInt();
Examples of correct code for the default "always"
option:
/*eslint radix: "error"*/
var num = parseInt("071", 10);
var num = parseInt("071", 8);
var num = parseFloat(someValue);
as-needed
Examples of incorrect code for the "as-needed"
option:
/*eslint radix: ["error", "as-needed"]*/
var num = parseInt("071", 10);
var num = parseInt("071", "abc");
var num = parseInt();
Examples of correct code for the "as-needed"
option:
/*eslint radix: ["error", "as-needed"]*/
var num = parseInt("071");
var num = parseInt("071", 8);
var num = parseFloat(someValue);
When Not To Use It
If you don't want to enforce either presence or omission of the 10
radix value you can turn this rule off.
Further Reading
Unnecessary semicolon. Open
};
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disallow unnecessary semicolons (no-extra-semi)
Typing mistakes and misunderstandings about where semicolons are required can lead to semicolons that are unnecessary. While not technically an error, extra semicolons can cause confusion when reading code.
Rule Details
This rule disallows unnecessary semicolons.
Examples of incorrect code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;;
function foo() {
// code
};
Examples of correct code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;
var foo = function() {
// code
};
When Not To Use It
If you intentionally use extra semicolons then you can disable this rule.
Related Rules
- [semi](semi.md)
- [semi-spacing](semi-spacing.md) Source: http://eslint.org/docs/rules/
Unexpected prompt. Open
input = prompt("Who would you like to add as a coauthor?", "Username");
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Disallow Use of Alert (no-alert)
JavaScript's alert
, confirm
, and prompt
functions are widely considered to be obtrusive as UI elements and should be replaced by a more appropriate custom UI implementation. Furthermore, alert
is often used while debugging code, which should be removed before deployment to production.
alert("here!");
Rule Details
This rule is aimed at catching debugging code that should be removed and popup UI elements that should be replaced with less obtrusive, custom UIs. As such, it will warn when it encounters alert
, prompt
, and confirm
function calls which are not shadowed.
Examples of incorrect code for this rule:
/*eslint no-alert: "error"*/
alert("here!");
confirm("Are you sure?");
prompt("What's your name?", "John Doe");
Examples of correct code for this rule:
/*eslint no-alert: "error"*/
customAlert("Something happened!");
customConfirm("Are you sure?");
customPrompt("Who are you?");
function foo() {
var alert = myCustomLib.customAlert;
alert();
}
Related Rules
- [no-console](no-console.md)
- [no-debugger](no-debugger.md) Source: http://eslint.org/docs/rules/
'input' is already defined. Open
var input = prompt("Add a template for the comment field to guide responses; enter the name (i.e. 'survey-template' for /wiki/survey-template) of a wiki page to use as the template:", "wiki-template-name");
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disallow variable redeclaration (no-redeclare)
In JavaScript, it's possible to redeclare the same variable name using var
. This can lead to confusion as to where the variable is actually declared and initialized.
Rule Details
This rule is aimed at eliminating variables that have multiple declarations in the same scope.
Examples of incorrect code for this rule:
/*eslint no-redeclare: "error"*/
var a = 3;
var a = 10;
Examples of correct code for this rule:
/*eslint no-redeclare: "error"*/
var a = 3;
// ...
a = 10;
Options
This rule takes one optional argument, an object with a boolean property "builtinGlobals"
. It defaults to false
.
If set to true
, this rule also checks redeclaration of built-in globals, such as Object
, Array
, Number
...
builtinGlobals
Examples of incorrect code for the { "builtinGlobals": true }
option:
/*eslint no-redeclare: ["error", { "builtinGlobals": true }]*/
var Object = 0;
Examples of incorrect code for the { "builtinGlobals": true }
option and the browser
environment:
/*eslint no-redeclare: ["error", { "builtinGlobals": true }]*/
/*eslint-env browser*/
var top = 0;
The browser
environment has many built-in global variables (for example, top
). Some of built-in global variables cannot be redeclared.
Source: http://eslint.org/docs/rules/
Align the elements of a hash literal if they span more than one line. Open
comment_via: comment_via_status,
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Check that the keys, separators, and values of a multi-line hash literal are aligned according to configuration. The configuration options are:
- key (left align keys)
- separator (align hash rockets and colons, right align keys)
- table (left align keys, hash rockets, and values)
The treatment of hashes passed as the last argument to a method call can also be configured. The options are:
- always_inspect
- always_ignore
- ignore_implicit (without curly braces)
- ignore_explicit (with curly braces)
Example:
# EnforcedHashRocketStyle: key (default)
# EnforcedColonStyle: key (default)
# good
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
# bad
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
Example:
# EnforcedHashRocketStyle: separator
# EnforcedColonStyle: separator
#good
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
#bad
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
{
:foo => bar,
:ba => baz
}
Example:
# EnforcedHashRocketStyle: table
# EnforcedColonStyle: table
#good
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
#bad
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
Align the elements of a hash literal if they span more than one line. Open
body: params[:body])
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Check that the keys, separators, and values of a multi-line hash literal are aligned according to configuration. The configuration options are:
- key (left align keys)
- separator (align hash rockets and colons, right align keys)
- table (left align keys, hash rockets, and values)
The treatment of hashes passed as the last argument to a method call can also be configured. The options are:
- always_inspect
- always_ignore
- ignore_implicit (without curly braces)
- ignore_explicit (with curly braces)
Example:
# EnforcedHashRocketStyle: key (default)
# EnforcedColonStyle: key (default)
# good
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
# bad
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
Example:
# EnforcedHashRocketStyle: separator
# EnforcedColonStyle: separator
#good
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
#bad
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
{
:foo => bar,
:ba => baz
}
Example:
# EnforcedHashRocketStyle: table
# EnforcedColonStyle: table
#good
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
#bad
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
Use %w
or %W
for an array of words. Open
elsif user.first_time_poster && !(user.username == self.author.username || self.coauthors&.exists?(username: user.username) || (['admin', 'moderator'].include? user.role))
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This cop can check for array literals made up of word-like strings, that are not using the %w() syntax.
Alternatively, it can check for uses of the %w() syntax, in projects which do not want to include that syntax.
Configuration option: MinSize
If set, arrays with fewer elements than this value will not trigger the
cop. For example, a MinSize
of 3
will not enforce a style on an
array of 2 or fewer elements.
Example: EnforcedStyle: percent (default)
# good
%w[foo bar baz]
# bad
['foo', 'bar', 'baz']
Example: EnforcedStyle: brackets
# good
['foo', 'bar', 'baz']
# bad
%w[foo bar baz]
Trailing whitespace detected. Open
redirect_to '/dashboard'
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'lng' is already defined. Open
var lng = document.getElementById(lng);
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disallow variable redeclaration (no-redeclare)
In JavaScript, it's possible to redeclare the same variable name using var
. This can lead to confusion as to where the variable is actually declared and initialized.
Rule Details
This rule is aimed at eliminating variables that have multiple declarations in the same scope.
Examples of incorrect code for this rule:
/*eslint no-redeclare: "error"*/
var a = 3;
var a = 10;
Examples of correct code for this rule:
/*eslint no-redeclare: "error"*/
var a = 3;
// ...
a = 10;
Options
This rule takes one optional argument, an object with a boolean property "builtinGlobals"
. It defaults to false
.
If set to true
, this rule also checks redeclaration of built-in globals, such as Object
, Array
, Number
...
builtinGlobals
Examples of incorrect code for the { "builtinGlobals": true }
option:
/*eslint no-redeclare: ["error", { "builtinGlobals": true }]*/
var Object = 0;
Examples of incorrect code for the { "builtinGlobals": true }
option and the browser
environment:
/*eslint no-redeclare: ["error", { "builtinGlobals": true }]*/
/*eslint-env browser*/
var top = 0;
The browser
environment has many built-in global variables (for example, top
). Some of built-in global variables cannot be redeclared.
Source: http://eslint.org/docs/rules/
Parsing error: 'import' and 'export' may appear only with 'sourceType: module' Open
import React from "react";
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For more information visit Source: http://eslint.org/docs/rules/
Align the elements of a hash literal if they span more than one line. Open
title: params[:title],
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Check that the keys, separators, and values of a multi-line hash literal are aligned according to configuration. The configuration options are:
- key (left align keys)
- separator (align hash rockets and colons, right align keys)
- table (left align keys, hash rockets, and values)
The treatment of hashes passed as the last argument to a method call can also be configured. The options are:
- always_inspect
- always_ignore
- ignore_implicit (without curly braces)
- ignore_explicit (with curly braces)
Example:
# EnforcedHashRocketStyle: key (default)
# EnforcedColonStyle: key (default)
# good
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
# bad
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
Example:
# EnforcedHashRocketStyle: separator
# EnforcedColonStyle: separator
#good
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
#bad
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
{
:foo => bar,
:ba => baz
}
Example:
# EnforcedHashRocketStyle: table
# EnforcedColonStyle: table
#good
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
#bad
{
foo: bar,
ba: baz
}
{
:foo => bar,
:ba => baz
}
Trailing whitespace detected. Open
@users = User.where(email: params[:address])
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Use the return of the conditional for variable assignment and comparison. Open
if params[:include_banned]
@users = User.where(email: params[:address])
.where('created_at > (?)', DateTime.new(2015)) # since 2015, whether banned or not
else
@users = User.where(email: params[:address])
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Expected '===' and instead saw '=='. Open
var should_fill_cell = cell.id == this.focused_cell_id;
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Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Unnecessary semicolon. Open
};
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disallow unnecessary semicolons (no-extra-semi)
Typing mistakes and misunderstandings about where semicolons are required can lead to semicolons that are unnecessary. While not technically an error, extra semicolons can cause confusion when reading code.
Rule Details
This rule disallows unnecessary semicolons.
Examples of incorrect code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;;
function foo() {
// code
};
Examples of correct code for this rule:
/*eslint no-extra-semi: "error"*/
var x = 5;
var foo = function() {
// code
};
When Not To Use It
If you intentionally use extra semicolons then you can disable this rule.
Related Rules
- [semi](semi.md)
- [semi-spacing](semi-spacing.md) Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
if (e.which == 32 || e.which == 13) publish()
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- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Expected '===' and instead saw '=='. Open
if(bulk == "batch_delete" || bulk == "batch_comment/delete") {
- Read upRead up
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- Exclude checks
Require === and !== (eqeqeq)
It is considered good practice to use the type-safe equality operators ===
and !==
instead of their regular counterparts ==
and !=
.
The reason for this is that ==
and !=
do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm.
For instance, the following statements are all considered true
:
[] == false
[] == ![]
3 == "03"
If one of those occurs in an innocent-looking statement such as a == b
the actual problem is very difficult to spot.
Rule Details
This rule is aimed at eliminating the type-unsafe equality operators.
Examples of incorrect code for this rule:
/*eslint eqeqeq: "error"*/
if (x == 42) { }
if ("" == text) { }
if (obj.getStuff() != undefined) { }
The --fix
option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof
expression, or if both operands are literals with the same type.
Options
always
The "always"
option (default) enforces the use of ===
and !==
in every situation (except when you opt-in to more specific handling of null
[see below]).
Examples of incorrect code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
Examples of correct code for the "always"
option:
/*eslint eqeqeq: ["error", "always"]*/
a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null
This rule optionally takes a second argument, which should be an object with the following supported properties:
-
"null"
: Customize how this rule treatsnull
literals. Possible values:-
always
(default) - Always use === or !==. -
never
- Never use === or !== withnull
. -
ignore
- Do not apply this rule tonull
.
-
smart
The "smart"
option enforces the use of ===
and !==
except for these cases:
- Comparing two literal values
- Evaluating the value of
typeof
- Comparing against
null
Examples of incorrect code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
// comparing two variables requires ===
a == b
// only one side is a literal
foo == true
bananas != 1
// comparing to undefined requires ===
value == undefined
Examples of correct code for the "smart"
option:
/*eslint eqeqeq: ["error", "smart"]*/
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null
allow-null
Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null
literal.
["error", "always", {"null": "ignore"}]
When Not To Use It
If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/
Parsing error: 'import' and 'export' may appear only with 'sourceType: module' Open
import React from "react";
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For more information visit Source: http://eslint.org/docs/rules/