Function parse
has 108 lines of code (exceeds 25 allowed). Consider refactoring. Open
function parse(s, env) {
var chunker = new RegExp([
'(' + CONTROL + ')', // control chars
'(' + BAREWORD + '|' + SINGLE_QUOTE + '|' + DOUBLE_QUOTE + ')*'
].join('|'), 'g');
Function has a complexity of 20. Open
return map(match, function(s) {
- Read upRead up
- Exclude checks
Limit Cyclomatic Complexity (complexity)
Cyclomatic complexity measures the number of linearly independent paths through a program's source code. This rule allows setting a cyclomatic complexity threshold.
function a(x) {
if (true) {
return x; // 1st path
} else if (false) {
return x+1; // 2nd path
} else {
return 4; // 3rd path
}
}
Rule Details
This rule is aimed at reducing code complexity by capping the amount of cyclomatic complexity allowed in a program. As such, it will warn when the cyclomatic complexity crosses the configured threshold (default is 20
).
Examples of incorrect code for a maximum of 2:
/*eslint complexity: ["error", 2]*/
function a(x) {
if (true) {
return x;
} else if (false) {
return x+1;
} else {
return 4; // 3rd path
}
}
Examples of correct code for a maximum of 2:
/*eslint complexity: ["error", 2]*/
function a(x) {
if (true) {
return x;
} else {
return 4;
}
}
Options
Optionally, you may specify a max
object property:
"complexity": ["error", 2]
is equivalent to
"complexity": ["error", { "max": 2 }]
Deprecated: the object property maximum
is deprecated. Please use the property max
instead.
When Not To Use It
If you can't determine an appropriate complexity limit for your code, then it's best to disable this rule.
Further Reading
Related Rules
- [max-depth](max-depth.md)
- [max-len](max-len.md)
- [max-nested-callbacks](max-nested-callbacks.md)
- [max-params](max-params.md)
- [max-statements](max-statements.md) Source: http://eslint.org/docs/rules/
Function parseEnvVar
has 28 lines of code (exceeds 25 allowed). Consider refactoring. Open
function parseEnvVar() {
i += 1;
var varend;
var varname;
Function parse
has a Cognitive Complexity of 9 (exceeds 5 allowed). Consider refactoring. Open
function parse(s, env) {
var chunker = new RegExp([
'(' + CONTROL + ')', // control chars
'(' + BAREWORD + '|' + SINGLE_QUOTE + '|' + DOUBLE_QUOTE + ')*'
].join('|'), 'g');
- Read upRead up
Cognitive Complexity
Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.
A method's cognitive complexity is based on a few simple rules:
- Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
- Code is considered more complex for each "break in the linear flow of the code"
- Code is considered more complex when "flow breaking structures are nested"
Further reading
Avoid deeply nested control flow statements. Open
} else if (c === DS) {
out += parseEnvVar();
} else {
out += c;
}
Avoid deeply nested control flow statements. Open
if (c === DQ || c === BS || c === DS) {
out += c;
} else {
out += BS + c;
}
Function quote
has a Cognitive Complexity of 7 (exceeds 5 allowed). Consider refactoring. Open
ShellQuote.quote = function(xs) {
return map(xs, function(s) {
if (s && typeof s === 'object') {
return s.op.replace(/(.)/g, '\\$1');
} else if (/["\s]/.test(s) && !/'/.test(s)) {
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Cognitive Complexity
Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.
A method's cognitive complexity is based on a few simple rules:
- Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
- Code is considered more complex for each "break in the linear flow of the code"
- Code is considered more complex when "flow breaking structures are nested"
Further reading
'parseEnvVar' was used before it was defined. Open
out += parseEnvVar();
- Read upRead up
- Exclude checks
Disallow Early Use (no-use-before-define)
In JavaScript, prior to ES6, variable and function declarations are hoisted to the top of a scope, so it's possible to use identifiers before their formal declarations in code. This can be confusing and some believe it is best to always declare variables and functions before using them.
In ES6, block-level bindings (let
and const
) introduce a "temporal dead zone" where a ReferenceError
will be thrown with any attempt to access the variable before its declaration.
Rule Details
This rule will warn when it encounters a reference to an identifier that has not yet been declared.
Examples of incorrect code for this rule:
/*eslint no-use-before-define: "error"*/
/*eslint-env es6*/
alert(a);
var a = 10;
f();
function f() {}
function g() {
return b;
}
var b = 1;
// With blockBindings: true
{
alert(c);
let c = 1;
}
Examples of correct code for this rule:
/*eslint no-use-before-define: "error"*/
/*eslint-env es6*/
var a;
a = 10;
alert(a);
function f() {}
f(1);
var b = 1;
function g() {
return b;
}
// With blockBindings: true
{
let C;
c++;
}
Options
{
"no-use-before-define": ["error", { "functions": true, "classes": true }]
}
-
functions
(boolean
) - The flag which shows whether or not this rule checks function declarations. If this istrue
, this rule warns every reference to a function before the function declaration. Otherwise, ignores those references. Function declarations are hoisted, so it's safe. Default istrue
. -
classes
(boolean
) - The flag which shows whether or not this rule checks class declarations of upper scopes. If this istrue
, this rule warns every reference to a class before the class declaration. Otherwise, ignores those references if the declaration is in upper function scopes. Class declarations are not hoisted, so it might be danger. Default istrue
. -
variables
(boolean
) - This flag determines whether or not the rule checks variable declarations in upper scopes. If this istrue
, the rule warns every reference to a variable before the variable declaration. Otherwise, the rule ignores a reference if the declaration is in an upper scope, while still reporting the reference if it's in the same scope as the declaration. Default istrue
.
This rule accepts "nofunc"
string as an option.
"nofunc"
is the same as { "functions": false, "classes": true }
.
functions
Examples of correct code for the { "functions": false }
option:
/*eslint no-use-before-define: ["error", { "functions": false }]*/
f();
function f() {}
classes
Examples of incorrect code for the { "classes": false }
option:
/*eslint no-use-before-define: ["error", { "classes": false }]*/
/*eslint-env es6*/
new A();
class A {
}
Examples of correct code for the { "classes": false }
option:
/*eslint no-use-before-define: ["error", { "classes": false }]*/
/*eslint-env es6*/
function foo() {
return new A();
}
class A {
}
variables
Examples of incorrect code for the { "variables": false }
option:
/*eslint no-use-before-define: ["error", { "variables": false }]*/
console.log(foo);
var foo = 1;
Examples of correct code for the { "variables": false }
option:
/*eslint no-use-before-define: ["error", { "variables": false }]*/
function baz() {
console.log(foo);
}
var foo = 1;
Source: http://eslint.org/docs/rules/
'parseEnvVar' was used before it was defined. Open
out += parseEnvVar();
- Read upRead up
- Exclude checks
Disallow Early Use (no-use-before-define)
In JavaScript, prior to ES6, variable and function declarations are hoisted to the top of a scope, so it's possible to use identifiers before their formal declarations in code. This can be confusing and some believe it is best to always declare variables and functions before using them.
In ES6, block-level bindings (let
and const
) introduce a "temporal dead zone" where a ReferenceError
will be thrown with any attempt to access the variable before its declaration.
Rule Details
This rule will warn when it encounters a reference to an identifier that has not yet been declared.
Examples of incorrect code for this rule:
/*eslint no-use-before-define: "error"*/
/*eslint-env es6*/
alert(a);
var a = 10;
f();
function f() {}
function g() {
return b;
}
var b = 1;
// With blockBindings: true
{
alert(c);
let c = 1;
}
Examples of correct code for this rule:
/*eslint no-use-before-define: "error"*/
/*eslint-env es6*/
var a;
a = 10;
alert(a);
function f() {}
f(1);
var b = 1;
function g() {
return b;
}
// With blockBindings: true
{
let C;
c++;
}
Options
{
"no-use-before-define": ["error", { "functions": true, "classes": true }]
}
-
functions
(boolean
) - The flag which shows whether or not this rule checks function declarations. If this istrue
, this rule warns every reference to a function before the function declaration. Otherwise, ignores those references. Function declarations are hoisted, so it's safe. Default istrue
. -
classes
(boolean
) - The flag which shows whether or not this rule checks class declarations of upper scopes. If this istrue
, this rule warns every reference to a class before the class declaration. Otherwise, ignores those references if the declaration is in upper function scopes. Class declarations are not hoisted, so it might be danger. Default istrue
. -
variables
(boolean
) - This flag determines whether or not the rule checks variable declarations in upper scopes. If this istrue
, the rule warns every reference to a variable before the variable declaration. Otherwise, the rule ignores a reference if the declaration is in an upper scope, while still reporting the reference if it's in the same scope as the declaration. Default istrue
.
This rule accepts "nofunc"
string as an option.
"nofunc"
is the same as { "functions": false, "classes": true }
.
functions
Examples of correct code for the { "functions": false }
option:
/*eslint no-use-before-define: ["error", { "functions": false }]*/
f();
function f() {}
classes
Examples of incorrect code for the { "classes": false }
option:
/*eslint no-use-before-define: ["error", { "classes": false }]*/
/*eslint-env es6*/
new A();
class A {
}
Examples of correct code for the { "classes": false }
option:
/*eslint no-use-before-define: ["error", { "classes": false }]*/
/*eslint-env es6*/
function foo() {
return new A();
}
class A {
}
variables
Examples of incorrect code for the { "variables": false }
option:
/*eslint no-use-before-define: ["error", { "variables": false }]*/
console.log(foo);
var foo = 1;
Examples of correct code for the { "variables": false }
option:
/*eslint no-use-before-define: ["error", { "variables": false }]*/
function baz() {
console.log(foo);
}
var foo = 1;
Source: http://eslint.org/docs/rules/
'varname' is assigned a value but never used. Open
var varname = false;
- Read upRead up
- Exclude checks
Disallow Unused Variables (no-unused-vars)
Variables that are declared and not used anywhere in the code are most likely an error due to incomplete refactoring. Such variables take up space in the code and can lead to confusion by readers.
Rule Details
This rule is aimed at eliminating unused variables, functions, and parameters of functions.
A variable is considered to be used if any of the following are true:
- It represents a function that is called (
doSomething()
) - It is read (
var y = x
) - It is passed into a function as an argument (
doSomething(x)
) - It is read inside of a function that is passed to another function (
doSomething(function() { foo(); })
)
A variable is not considered to be used if it is only ever assigned to (var x = 5
) or declared.
Examples of incorrect code for this rule:
/*eslint no-unused-vars: "error"*/
/*global some_unused_var*/
// It checks variables you have defined as global
some_unused_var = 42;
var x;
// Write-only variables are not considered as used.
var y = 10;
y = 5;
// A read for a modification of itself is not considered as used.
var z = 0;
z = z + 1;
// By default, unused arguments cause warnings.
(function(foo) {
return 5;
})();
// Unused recursive functions also cause warnings.
function fact(n) {
if (n < 2) return 1;
return n * fact(n - 1);
}
// When a function definition destructures an array, unused entries from the array also cause warnings.
function getY([x, y]) {
return y;
}
Examples of correct code for this rule:
/*eslint no-unused-vars: "error"*/
var x = 10;
alert(x);
// foo is considered used here
myFunc(function foo() {
// ...
}.bind(this));
(function(foo) {
return foo;
})();
var myFunc;
myFunc = setTimeout(function() {
// myFunc is considered used
myFunc();
}, 50);
// Only the second argument from the descructured array is used.
function getY([, y]) {
return y;
}
exported
In environments outside of CommonJS or ECMAScript modules, you may use var
to create a global variable that may be used by other scripts. You can use the /* exported variableName */
comment block to indicate that this variable is being exported and therefore should not be considered unused.
Note that /* exported */
has no effect for any of the following:
- when the environment is
node
orcommonjs
- when
parserOptions.sourceType
ismodule
- when
ecmaFeatures.globalReturn
istrue
The line comment // exported variableName
will not work as exported
is not line-specific.
Examples of correct code for /* exported variableName */
operation:
/* exported global_var */
var global_var = 42;
Options
This rule takes one argument which can be a string or an object. The string settings are the same as those of the vars
property (explained below).
By default this rule is enabled with all
option for variables and after-used
for arguments.
{
"rules": {
"no-unused-vars": ["error", { "vars": "all", "args": "after-used", "ignoreRestSiblings": false }]
}
}
vars
The vars
option has two settings:
-
all
checks all variables for usage, including those in the global scope. This is the default setting. -
local
checks only that locally-declared variables are used but will allow global variables to be unused.
vars: local
Examples of correct code for the { "vars": "local" }
option:
/*eslint no-unused-vars: ["error", { "vars": "local" }]*/
/*global some_unused_var */
some_unused_var = 42;
varsIgnorePattern
The varsIgnorePattern
option specifies exceptions not to check for usage: variables whose names match a regexp pattern. For example, variables whose names contain ignored
or Ignored
.
Examples of correct code for the { "varsIgnorePattern": "[iI]gnored" }
option:
/*eslint no-unused-vars: ["error", { "varsIgnorePattern": "[iI]gnored" }]*/
var firstVarIgnored = 1;
var secondVar = 2;
console.log(secondVar);
args
The args
option has three settings:
-
after-used
- only the last argument must be used. This allows you, for instance, to have two named parameters to a function and as long as you use the second argument, ESLint will not warn you about the first. This is the default setting. -
all
- all named arguments must be used. -
none
- do not check arguments.
args: after-used
Examples of incorrect code for the default { "args": "after-used" }
option:
/*eslint no-unused-vars: ["error", { "args": "after-used" }]*/
// 1 error
// "baz" is defined but never used
(function(foo, bar, baz) {
return bar;
})();
Examples of correct code for the default { "args": "after-used" }
option:
/*eslint no-unused-vars: ["error", {"args": "after-used"}]*/
(function(foo, bar, baz) {
return baz;
})();
args: all
Examples of incorrect code for the { "args": "all" }
option:
/*eslint no-unused-vars: ["error", { "args": "all" }]*/
// 2 errors
// "foo" is defined but never used
// "baz" is defined but never used
(function(foo, bar, baz) {
return bar;
})();
args: none
Examples of correct code for the { "args": "none" }
option:
/*eslint no-unused-vars: ["error", { "args": "none" }]*/
(function(foo, bar, baz) {
return bar;
})();
ignoreRestSiblings
The ignoreRestSiblings
option is a boolean (default: false
). Using a Rest Property it is possible to "omit" properties from an object, but by default the sibling properties are marked as "unused". With this option enabled the rest property's siblings are ignored.
Examples of correct code for the { "ignoreRestSiblings": true }
option:
/*eslint no-unused-vars: ["error", { "ignoreRestSiblings": true }]*/
// 'type' is ignored because it has a rest property sibling.
var { type, ...coords } = data;
argsIgnorePattern
The argsIgnorePattern
option specifies exceptions not to check for usage: arguments whose names match a regexp pattern. For example, variables whose names begin with an underscore.
Examples of correct code for the { "argsIgnorePattern": "^_" }
option:
/*eslint no-unused-vars: ["error", { "argsIgnorePattern": "^_" }]*/
function foo(x, _y) {
return x + 1;
}
foo();
caughtErrors
The caughtErrors
option is used for catch
block arguments validation.
It has two settings:
-
none
- do not check error objects. This is the default setting. -
all
- all named arguments must be used.
caughtErrors: none
Not specifying this rule is equivalent of assigning it to none
.
Examples of correct code for the { "caughtErrors": "none" }
option:
/*eslint no-unused-vars: ["error", { "caughtErrors": "none" }]*/
try {
//...
} catch (err) {
console.error("errors");
}
caughtErrors: all
Examples of incorrect code for the { "caughtErrors": "all" }
option:
/*eslint no-unused-vars: ["error", { "caughtErrors": "all" }]*/
// 1 error
// "err" is defined but never used
try {
//...
} catch (err) {
console.error("errors");
}
caughtErrorsIgnorePattern
The caughtErrorsIgnorePattern
option specifies exceptions not to check for usage: catch arguments whose names match a regexp pattern. For example, variables whose names begin with a string 'ignore'.
Examples of correct code for the { "caughtErrorsIgnorePattern": "^ignore" }
option:
/*eslint no-unused-vars: ["error", { "caughtErrorsIgnorePattern": "^ignore" }]*/
try {
//...
} catch (ignoreErr) {
console.error("errors");
}
When Not To Use It
If you don't want to be notified about unused variables or function arguments, you can safely turn this rule off. Source: http://eslint.org/docs/rules/