For detailed explanation on how things work, checkout the [guide](http://vuejs-templates.github.io/webpack/) and [docs for vue-loader](http://vuejs.github.io/vue-loader).
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"
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"
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"
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 46.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 46.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 46.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 45.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 45.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
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"
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"
There are several common guidelines which require specific indentation of nested blocks and statements, like:
functionhello(indentSize, type){
if(indentSize ===4&& type !=='tab'){
console.log('Each next indentation will increase on 4 spaces');
}
}
These are the most common scenarios recommended in different style guides:
Two spaces, not longer and no tabs: Google, npm, Node.js, Idiomatic, Felix
Tabs: jQuery
Four spaces: Crockford
Rule Details
This rule enforces a consistent indentation style. The default style is 4 spaces.
Options
This rule has a mixed option:
For example, for 2-space indentation:
{
"indent": ["error", 2]
}
Or for tabbed indentation:
{
"indent": ["error", "tab"]
}
Examples of incorrect code for this rule with the default options:
/*eslint indent: "error"*/
if(a){
b=c;
functionfoo(d){
e=f;
}
}
Examples of correct code for this rule with the default options:
/*eslint indent: "error"*/
if(a){
b=c;
functionfoo(d){
e=f;
}
}
This rule has an object option:
"SwitchCase" (default: 0) enforces indentation level for case clauses in switch statements
"VariableDeclarator" (default: 1) enforces indentation level for var declarators; can also take an object to define separate rules for var, let and const declarations.
"outerIIFEBody" (default: 1) enforces indentation level for file-level IIFEs.
"MemberExpression" (off by default) enforces indentation level for multi-line property chains (except in variable declarations and assignments)
"FunctionDeclaration" takes an object to define rules for function declarations.
parameters (off by default) enforces indentation level for parameters in a function declaration. This can either be a number indicating indentation level, or the string "first" indicating that all parameters of the declaration must be aligned with the first parameter.
body (default: 1) enforces indentation level for the body of a function declaration.
"FunctionExpression" takes an object to define rules for function expressions.
parameters (off by default) enforces indentation level for parameters in a function expression. This can either be a number indicating indentation level, or the string "first" indicating that all parameters of the expression must be aligned with the first parameter.
body (default: 1) enforces indentation level for the body of a function expression.
"CallExpression" takes an object to define rules for function call expressions.
arguments (off by default) enforces indentation level for arguments in a call expression. This can either be a number indicating indentation level, or the string "first" indicating that all arguments of the expression must be aligned with the first argument.
"ArrayExpression" (default: 1) enforces indentation level for elements in arrays. It can also be set to the string "first", indicating that all the elements in the array should be aligned with the first element.
"ObjectExpression" (default: 1) enforces indentation level for properties in objects. It can be set to the string "first", indicating that all properties in the object should be aligned with the first property.
Level of indentation denotes the multiple of the indent specified. Example:
Indent of 4 spaces with VariableDeclarator set to 2 will indent the multi-line variable declarations with 8 spaces.
Indent of 2 spaces with VariableDeclarator set to 2 will indent the multi-line variable declarations with 4 spaces.
Indent of 2 spaces with VariableDeclarator set to {"var": 2, "let": 2, "const": 3} will indent the multi-line variable declarations with 4 spaces for var and let, 6 spaces for const statements.
Indent of tab with VariableDeclarator set to 2 will indent the multi-line variable declarations with 2 tabs.
Indent of 2 spaces with SwitchCase set to 0 will not indent case clauses with respect to switch statements.
Indent of 2 spaces with SwitchCase set to 1 will indent case clauses with 2 spaces with respect to switch statements.
Indent of 2 spaces with SwitchCase set to 2 will indent case clauses with 4 spaces with respect to switch statements.
Indent of tab with SwitchCase set to 2 will indent case clauses with 2 tabs with respect to switch statements.
Indent of 2 spaces with MemberExpression set to 0 will indent the multi-line property chains with 0 spaces.
Indent of 2 spaces with MemberExpression set to 1 will indent the multi-line property chains with 2 spaces.
Indent of 2 spaces with MemberExpression set to 2 will indent the multi-line property chains with 4 spaces.
Indent of 4 spaces with MemberExpression set to 0 will indent the multi-line property chains with 0 spaces.
Indent of 4 spaces with MemberExpression set to 1 will indent the multi-line property chains with 4 spaces.
Indent of 4 spaces with MemberExpression set to 2 will indent the multi-line property chains with 8 spaces.
tab
Examples of incorrect code for this rule with the "tab" option:
/*eslint indent: ["error", "tab"]*/
if(a){
b=c;
functionfoo(d){
e=f;
}
}
Examples of correct code for this rule with the "tab" option:
/*eslint indent: ["error", "tab"]*/
if(a){
/*tab*/b=c;
/*tab*/functionfoo(d){
/*tab*//*tab*/e=f;
/*tab*/}
}
SwitchCase
Examples of incorrect code for this rule with the 2, { "SwitchCase": 1 } options:
This rule is triggered when there are lines that are longer than the
configured line length (default: 80 characters). To fix this, split the line
up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured
line length. This allows you to still include items such as long URLs without
being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a
requirement for document readability, and tentatively compatible with code
rules. Still, some languages do not lend themselves to short lines.
enforce consistent indentation (indent)
There are several common guidelines which require specific indentation of nested blocks and statements, like:
functionhello(indentSize, type){
if(indentSize ===4&& type !=='tab'){
console.log('Each next indentation will increase on 4 spaces');
}
}
These are the most common scenarios recommended in different style guides:
Two spaces, not longer and no tabs: Google, npm, Node.js, Idiomatic, Felix
Tabs: jQuery
Four spaces: Crockford
Rule Details
This rule enforces a consistent indentation style. The default style is 4 spaces.
Options
This rule has a mixed option:
For example, for 2-space indentation:
{
"indent": ["error", 2]
}
Or for tabbed indentation:
{
"indent": ["error", "tab"]
}
Examples of incorrect code for this rule with the default options:
/*eslint indent: "error"*/
if(a){
b=c;
functionfoo(d){
e=f;
}
}
Examples of correct code for this rule with the default options:
/*eslint indent: "error"*/
if(a){
b=c;
functionfoo(d){
e=f;
}
}
This rule has an object option:
"SwitchCase" (default: 0) enforces indentation level for case clauses in switch statements
"VariableDeclarator" (default: 1) enforces indentation level for var declarators; can also take an object to define separate rules for var, let and const declarations.
"outerIIFEBody" (default: 1) enforces indentation level for file-level IIFEs.
"MemberExpression" (off by default) enforces indentation level for multi-line property chains (except in variable declarations and assignments)
"FunctionDeclaration" takes an object to define rules for function declarations.
parameters (off by default) enforces indentation level for parameters in a function declaration. This can either be a number indicating indentation level, or the string "first" indicating that all parameters of the declaration must be aligned with the first parameter.
body (default: 1) enforces indentation level for the body of a function declaration.
"FunctionExpression" takes an object to define rules for function expressions.
parameters (off by default) enforces indentation level for parameters in a function expression. This can either be a number indicating indentation level, or the string "first" indicating that all parameters of the expression must be aligned with the first parameter.
body (default: 1) enforces indentation level for the body of a function expression.
"CallExpression" takes an object to define rules for function call expressions.
arguments (off by default) enforces indentation level for arguments in a call expression. This can either be a number indicating indentation level, or the string "first" indicating that all arguments of the expression must be aligned with the first argument.
"ArrayExpression" (default: 1) enforces indentation level for elements in arrays. It can also be set to the string "first", indicating that all the elements in the array should be aligned with the first element.
"ObjectExpression" (default: 1) enforces indentation level for properties in objects. It can be set to the string "first", indicating that all properties in the object should be aligned with the first property.
Level of indentation denotes the multiple of the indent specified. Example:
Indent of 4 spaces with VariableDeclarator set to 2 will indent the multi-line variable declarations with 8 spaces.
Indent of 2 spaces with VariableDeclarator set to 2 will indent the multi-line variable declarations with 4 spaces.
Indent of 2 spaces with VariableDeclarator set to {"var": 2, "let": 2, "const": 3} will indent the multi-line variable declarations with 4 spaces for var and let, 6 spaces for const statements.
Indent of tab with VariableDeclarator set to 2 will indent the multi-line variable declarations with 2 tabs.
Indent of 2 spaces with SwitchCase set to 0 will not indent case clauses with respect to switch statements.
Indent of 2 spaces with SwitchCase set to 1 will indent case clauses with 2 spaces with respect to switch statements.
Indent of 2 spaces with SwitchCase set to 2 will indent case clauses with 4 spaces with respect to switch statements.
Indent of tab with SwitchCase set to 2 will indent case clauses with 2 tabs with respect to switch statements.
Indent of 2 spaces with MemberExpression set to 0 will indent the multi-line property chains with 0 spaces.
Indent of 2 spaces with MemberExpression set to 1 will indent the multi-line property chains with 2 spaces.
Indent of 2 spaces with MemberExpression set to 2 will indent the multi-line property chains with 4 spaces.
Indent of 4 spaces with MemberExpression set to 0 will indent the multi-line property chains with 0 spaces.
Indent of 4 spaces with MemberExpression set to 1 will indent the multi-line property chains with 4 spaces.
Indent of 4 spaces with MemberExpression set to 2 will indent the multi-line property chains with 8 spaces.
tab
Examples of incorrect code for this rule with the "tab" option:
/*eslint indent: ["error", "tab"]*/
if(a){
b=c;
functionfoo(d){
e=f;
}
}
Examples of correct code for this rule with the "tab" option:
/*eslint indent: ["error", "tab"]*/
if(a){
/*tab*/b=c;
/*tab*/functionfoo(d){
/*tab*//*tab*/e=f;
/*tab*/}
}
SwitchCase
Examples of incorrect code for this rule with the 2, { "SwitchCase": 1 } options: