jscs

JavaScript Style Checker

npm install jscs
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JSCS — JavaScript Code Style.

jscs is a code style checker. jscs can check cases, which are not implemented in jshint, but it does not duplicate jshint functionality, so you should use jscs and jshint together.

Friendly packages

Installation

jscs can be installed using npm:

npm install jscs

To run jscs, you can use the following command from the project root:

./node_modules/.bin/jscs path[ path[...]]

Configuration

jscs looks for configuration in the project root.

If there is a package.json then it will use the jscsConfig field of it if present, if there is no package.json, or the jscsConfig field is not found, jscs will look for a .jscsrc file, and finally a .jscs.json file for configuration.

requireCurlyBraces

Requires curly braces after statements.

Type: Array

Values: Arrow of quoted keywords

JSHint: curly

Example

"requireCurlyBraces": [
    "if",
    "else",
    "for",
    "while",
    "do",
    "try",
    "catch",
    "case",
    "default"
]
Valid
if (x) {
    x++;
}
Invalid
if (x) x++;

requireSpaceAfterKeywords

Requires space after keyword.

Type: Array

Values: Array of quoted keywords

Example

"requireSpaceAfterKeywords": [
    "if",
    "else",
    "for",
    "while",
    "do",
    "switch",
    "return",
    "try",
    "catch"
]
Valid
return true;
Invalid
if(x) {
    x++;
}

disallowSpaceAfterKeywords

Disallows space after keyword.

Type: Array

Values: Array of quoted keywords

Example

"disallowSpaceAfterKeywords": [
    "if",
    "else",
    "for",
    "while",
    "do",
    "switch",
    "try",
    "catch"
]
Valid
if(x > y) {
    y++;
}

requireParenthesesAroundIIFE

Requires parentheses around immediately invoked function expressions.

Type: Boolean

Values: true

JSHint: immed

Example

"requireParenthesesAroundIIFE": true
Valid
var a = (function(){ return 1; })();
var b = (function(){ return 2; }());
var c = (function(){ return 3; }).call(this, arg1);
var d = (function(){ return 3; }.call(this, arg1));
var e = (function(){ return d; }).apply(this, args);
var f = (function(){ return d; }.apply(this, args));
Invalid
var a = function(){ return 1; }();
var c = function(){ return 3; }.call(this, arg1);
var d = function(){ return d; }.apply(this, args);

requireSpacesInFunctionExpression

Requires space before () or {} in function declarations.

Type: Object

Values: beforeOpeningRoundBrace and beforeOpeningCurlyBrace as child properties. Child properties must be set to true.

Example

"requireSpacesInFunctionExpression": {
    "beforeOpeningRoundBrace": true,
    "beforeOpeningCurlyBrace": true
}
Valid
function () {}
function a () {}
Invalid
function() {}
function (){}

disallowSpacesInFunctionExpression

Disallows space before () or {} in function declarations and expressions (both named and anonymous).

Type: Object

Values: "beforeOpeningRoundBrace" and "beforeOpeningCurlyBrace" as child properties. Child properties must be set to true.

Example

"disallowSpacesInFunctionExpression": {
    "beforeOpeningRoundBrace": true,
    "beforeOpeningCurlyBrace": true
}
Valid
function(){}
function a(){}
Invalid
function () {}
function a (){}

requireSpacesInAnonymousFunctionExpression

Requires space before () or {} in anonymous function expressions.

Type: Object

Values: beforeOpeningRoundBrace and beforeOpeningCurlyBrace as child properties. Child properties must be set to true.

Example

"requireSpacesInAnonymousFunctionExpression": {
    "beforeOpeningRoundBrace": true,
    "beforeOpeningCurlyBrace": true
}
Valid
function () {}
Invalid
function() {}
function (){}

disallowSpacesInAnonymousFunctionExpression

Disallows space before () or {} in anonymous function expressions.

Type: Object

Values: "beforeOpeningRoundBrace" and "beforeOpeningCurlyBrace" as child properties. Child properties must be set to true.

Example

"disallowSpacesInAnonymousFunctionExpression": {
    "beforeOpeningRoundBrace": true,
    "beforeOpeningCurlyBrace": true
}
Valid
function(){}
Invalid
function () {}
function (){}

requireSpacesInNamedFunctionExpression

Requires space before () or {} in named function expressions.

Type: Object

Values: beforeOpeningRoundBrace and beforeOpeningCurlyBrace as child properties. Child properties must be set to true.

Example

"requireSpacesInNamedFunctionExpression": {
    "beforeOpeningRoundBrace": true,
    "beforeOpeningCurlyBrace": true
}
Valid
function a () {}
Invalid
function a() {}
function a(){}

disallowSpacesInNamedFunctionExpression

Disallows space before () or {} in named function expressions.

Type: Object

Values: "beforeOpeningRoundBrace" and "beforeOpeningCurlyBrace" as child properties. Child properties must be set to true.

Example

"disallowSpacesInNamedFunctionExpression": {
    "beforeOpeningRoundBrace": true,
    "beforeOpeningCurlyBrace": true
}
Valid
function a(){}
Invalid
function a () {}
function a (){}

requireSpacesInFunctionDeclaration

Requires space before () or {} in function declarations.

Type: Object

Values: beforeOpeningRoundBrace and beforeOpeningCurlyBrace as child properties. Child properties must be set to true.

Example

"requireSpacesInFunctionExpression": {
    "beforeOpeningRoundBrace": true,
    "beforeOpeningCurlyBrace": true
}
Valid
function a () {}
Invalid
function a() {}
function a (){}

disallowSpacesInFunctionDeclaration

Disallows space before () or {} in function declarations.

Type: Object

Values: "beforeOpeningRoundBrace" and "beforeOpeningCurlyBrace" as child properties. Child properties must be set to true.

Example

"disallowSpacesInFunctionExpression": {
    "beforeOpeningRoundBrace": true,
    "beforeOpeningCurlyBrace": true
}
Valid
function a(){}
Invalid
function a () {}
function a (){}

disallowMultipleVarDecl

Disallows multiple var declaration (except for-loop).

Type: Boolean

Values: true

JSHint: onevar

Example

"disallowMultipleVarDecl": true
Valid
var x = 1;
var y = 2;

for (var i = 0, j = arr.length; i < j; i++) {}
Invalid
var x = 1,
    y = 2;

requireMultipleVarDecl

Requires multiple var declaration.

Type: Boolean

Values: true

JSHint: onevar

Example

"requireMultipleVarDecl": true
Valid
var x = 1,
    y = 2;
Invalid
var x = 1;
var y = 2;

requireBlocksOnNewline

Requires blocks to begin and end with a newline

Type: Boolean

Values: true

Example

"requireBlocksOnNewline": true
Valid
if (true) {
    doSomething();
}
var abc = function() {};
Invalid
if (true) {doSomething();}

disallowEmptyBlocks

Disallows empty blocks (except for catch blocks).

Type: Boolean

Values: true

JSHint: noempty

Example

"disallowEmptyBlocks": true
Valid
if ( a == b ) { c = d; }
try { a = b; } catch( e ){}
Invalid
if ( a == b ) { } else { c = d; }

disallowSpacesInsideObjectBrackets

Disallows space after opening object curly brace and before closing.

Type: Boolean

Values: true

Example

"disallowSpacesInsideObjectBrackets": true
Valid
var x = {a: 1};
Invalid
var x = { a: 1 };

disallowSpacesInsideArrayBrackets

Disallows space after opening array square bracket and before closing.

Type: Boolean

Values: true

Example

"disallowSpacesInsideArrayBrackets": true
Valid
var x = [1];
Invalid
var x = [ 1 ];

disallowSpacesInsideParentheses

Disallows space after opening round bracket and before closing.

Type: Boolean

Values: true

Example

"disallowSpacesInsideParentheses": true
Valid
var x = (1 + 2) * 3;
Invalid
var x = ( 1 + 2 ) * 3;

requireSpacesInsideObjectBrackets

Requires space after opening object curly brace and before closing.

Type: String

Values: "all" for strict mode, "allButNested" ignores closing brackets in a row.

Example

"requireSpacesInsideObjectBrackets": "all"
Valid for mode "all"
var x = { a: { b: 1 } };
Valid for mode "allButNested"
var x = { a: { b: 1 }};
Invalid
var x = {a: 1};

requireSpacesInsideArrayBrackets

Requires space after opening array square bracket and before closing.

Type: String

Values: "all" for strict mode, "allButNested" ignores closing brackets in a row.

Example

"requireSpacesInsideArrayBrackets": "all"
Valid for mode "all"
var x = [ 1 ];
Valid for mode "allButNested"
var x = [[ 1 ], [ 2 ]];
Invalid
var x = [1];

disallowQuotedKeysInObjects

Disallows quoted keys in object if possible.

Type: String or Boolean

Values:

  • true for strict mode
  • "allButReserved" allows ES3+ reserved words to remain quoted which is helpful when using this option with JSHint's es3 flag.

Example

"disallowQuotedKeysInObjects": true
Valid for mode true
var x = { a: { default: 1 } };
Valid for mode "allButReserved"
var x = {a: 1, 'default': 2};
Invalid
var x = {'a': 1};

disallowDanglingUnderscores

Disallows identifiers that start or end in _, except for some popular exceptions:

  • _ (underscore.js)
  • __filename (node.js global)
  • __dirname (node.js global)

Type: Boolean

Values: true

JSHint: nomen

Example

"disallowDanglingUnderscores": true
Valid
var x = 1;
var y = _.extend;
var z = __dirname;
var w = __filename;
var x_y = 1;
Invalid
var _x = 1;
var x_ = 1;
var x_y_ = 1;

disallowSpaceAfterObjectKeys

Disallows space after object keys.

Type: Boolean

Values: true

Example

"disallowSpaceAfterObjectKeys": true
Valid
var x = {a: 1};
Invalid
var x = {a : 1};

requireSpaceAfterObjectKeys

Requires space after object keys.

Type: Boolean

Values: true

Example

"requireSpaceAfterObjectKeys": true
Valid
var x = {a : 1};
Invalid
var x = {a: 1};

disallowCommaBeforeLineBreak

Disallows commas as last token on a line in lists.

Type: Boolean

Values: true

JSHint: laxcomma

Example

"disallowCommaBeforeLineBreak": true
Valid
var x = {
    one: 1
    , two: 2
};
var y = { three: 3, four: 4};
Invalid
var x = {
    one: 1,
    two: 2
};

requireCommaBeforeLineBreak

Requires commas as last token on a line in lists.

Type: Boolean

Values: true

JSHint: laxcomma

Example

"requireCommaBeforeLineBreak": true
Valid
var x = {
    one: 1,
    two: 2
};
var y = { three: 3, four: 4};
Invalid
var x = {
    one: 1
    , two: 2
};

requireAlignedObjectValues

Requires proper alignment in object literals.

Type: String

Values:

- `"all"` for strict mode,
- `"skipWithFunction"` ignores objects if one of the property values is a function expression,
- `"skipWithLineBreak"` ignores objects if there are line breaks between properties

Example

"requireAlignedObjectValues": "all"
Valid
var x = {
    a   : 1,
    bcd : 2,
    ef  : 'str'
};
Invalid
var x = {
    a : 1,
    bcd : 2,
    ef : 'str'
};

requireOperatorBeforeLineBreak

Requires operators to appear before line breaks and not after.

Type: Array

Values: Array of quoted operators

JSHint: laxbreak

Example

"requireOperatorBeforeLineBreak": [
    "?",
    "+",
    "-",
    "/",
    "*",
    "=",
    "==",
    "===",
    "!=",
    "!==",
    ">",
    ">=",
    "<",
    "<="
]
Valid
x = y ? 1 : 2;
x = y ?
    1 : 2;
Invalid
x = y
    ? 1 : 2;

disallowLeftStickedOperators

Disallows sticking operators to the left.

Type: Array

Values: Array of quoted operators

Example

"disallowLeftStickedOperators": [
    "?",
    "+",
    "-",
    "/",
    "*",
    "=",
    "==",
    "===",
    "!=",
    "!==",
    ">",
    ">=",
    "<",
    "<="
]
Valid
x = y ? 1 : 2;
Invalid
x = y? 1 : 2;

requireRightStickedOperators

Requires sticking operators to the right.

Type: Array

Values: Array of quoted operators

Example

"requireRightStickedOperators": ["!"]
Valid
x = !y;
Invalid
x = ! y;

disallowRightStickedOperators

Disallows sticking operators to the right.

Type: Array

Values: Array of quoted operators

Example

"disallowRightStickedOperators": [
    "?",
    "+",
    "/",
    "*",
    ":",
    "=",
    "==",
    "===",
    "!=",
    "!==",
    ">",
    ">=",
    "<",
    "<="
]
Valid
x = y + 1;
Invalid
x = y +1;

requireLeftStickedOperators

Requires sticking operators to the left.

Type: Array

Values: Array of quoted operators

Example

"requireLeftStickedOperators": [","]
Valid
x = [1, 2];
Invalid
x = [1 , 2];

disallowSpaceAfterPrefixUnaryOperators

Requires sticking unary operators to the right.

Type: Array

Values: Array of quoted operators

Example

"disallowSpaceAfterPrefixUnaryOperators": ["++", "--", "+", "-", "~", "!"]
Valid
x = !y; y = ++z;
Invalid
x = ! y; y = ++ z;

requireSpaceAfterPrefixUnaryOperators

Disallows sticking unary operators to the right.

Type: Array

Values: Array of quoted operators

Example

"requireSpaceAfterPrefixUnaryOperators": ["++", "--", "+", "-", "~", "!"]
Valid
x = ! y; y = ++ z;
Invalid
x = !y; y = ++z;

disallowSpaceBeforePostfixUnaryOperators

Requires sticking unary operators to the left.

Type: Array

Values: Array of quoted operators

Example

"disallowSpaceBeforePostfixUnaryOperators": ["++", "--"]
Valid
x = y++; y = z--;
Invalid
x = y ++; y = z --;

requireSpaceBeforePostfixUnaryOperators

Disallows sticking unary operators to the left.

Type: Array

Values: Array of quoted operators

Example

"requireSpaceBeforePostfixUnaryOperators": ["++", "--"]
Valid
x = y ++; y = z --;
Invalid
x = y++; y = z--;

disallowSpaceBeforeBinaryOperators

Requires sticking binary operators to the left.

Type: Array

Values: Array of quoted operators

Example

"disallowSpaceBeforeBinaryOperators": [
    "+",
    "-",
    "/",
    "*",
    "=",
    "==",
    "===",
    "!=",
    "!=="
]
Valid
x+ y;
Invalid
x + y;

requireSpaceBeforeBinaryOperators

Disallows sticking binary operators to the left.

Type: Array

Values: Array of quoted operators

Example

"requireSpaceBeforeBinaryOperators": [
    "+",
    "-",
    "/",
    "*",
    "=",
    "==",
    "===",
    "!=",
    "!=="
]
Valid
x !== y;
Invalid
x!== y;

disallowSpaceAfterBinaryOperators

Requires sticking binary operators to the right.

Type: Array

Values: Array of quoted operators

Example

"disallowSpaceAfterBinaryOperators": [
    "+",
    "-",
    "/",
    "*",
    "=",
    "==",
    "===",
    "!=",
    "!=="
]
Valid
x +y;
Invalid
x+ y;

requireSpaceAfterBinaryOperators

Disallows sticking binary operators to the right.

Type: Array

Values: Array of quoted operators

Example

"requireSpaceAfterBinaryOperators": [
    "+",
    "-",
    "/",
    "*",
    "=",
    "==",
    "===",
    "!=",
    "!=="
]
Valid
x + y;
Invalid
x +y;

disallowImplicitTypeConversion

Disallows implicit type conversion.

Type: Array

Values: Array of quoted types

Example

"disallowImplicitTypeConversion": ["numeric", "boolean", "binary", "string"]
Valid
x = Boolean(y);
x = Number(y);
x = String(y);
x = s.indexOf('.') !== -1;
Invalid
x = !!y;
x = +y;
x = '' + y;
x = ~s.indexOf('.');

requireCamelCaseOrUpperCaseIdentifiers

Requires identifiers to be camelCased or UPPERCASE_WITH_UNDERSCORES

Type: Boolean

Values: true

JSHint: camelcase

Example

"requireCamelCaseOrUpperCaseIdentifiers": true
Valid
var camelCase = 0;
var CamelCase = 1;
var _camelCase = 2;
var camelCase_ = 3;
var UPPER_CASE = 4;
Invalid
var lower_case = 1;
var Mixed_case = 2;
var mixed_Case = 3;

disallowKeywords

Disallows usage of specified keywords.

Type: Array

Values: Array of quoted keywords

Example

"disallowKeywords": ["with"]
Invalid
with (x) {
    prop++;
}

disallowMultipleLineStrings

Disallows strings that span multiple lines without using concatenation.

Type: Boolean

Values: true

JSHint: multistr

Example

"disallowMultipleLineStrings": true
Valid
var x = "multi" +
        "line";
var y = "single line";
Invalid
var x = "multi \
        line";

disallowMultipleLineBreaks

Disallows multiple blank lines in a row.

Type: Boolean

Values: true

Example

"disallowMultipleLineBreaks": true
Valid
var x = 1;

x++;
Invalid
var x = 1;


x++;

validateLineBreaks

Option to check line break characters

Type: String

Values: "CR", "LF", "CRLF"

Example

"validateLineBreaks": "LF"
Valid
var x = 1;<LF>
x++;
Invalid
var x = 1;<CRLF>
x++;

validateQuoteMarks

Requires all quote marks to be either the supplied value, or consistent if true

Type: String or Object

Values:

  • "\"": all strings require double quotes
  • "'": all strings require single quotes
  • true: all strings require the quote mark first encountered in the source code
  • Object:
    • escape: allow the "other" quote mark to be used, but only to avoid having to escape
    • mark: the same effect as the non-object values

JSHint: quotmark

Example

"validateQuoteMarks": "\""
"validateQuoteMarks": { "mark": "\"", "escape": true }
Valid example for mode { "mark": "\"", "escape": true }
var x = "x";
var y = '"x"';
Invalid example for mode { "mark": "\"", "escape": true }
var x = "x";
var y = 'x';
Valid example for mode "\"" or mode true
var x = "x";
Valid example for mode "'" or mode true
var x = 'x';
Invalid example for mode true
var x = "x", y = 'y';

validateIndentation

Validates indentation for arrays, objects, switch statements, and block statements

Type: Integer or String

Values: A positive integer or "\t"

JSHint: indent

Example

"validateIndentation": "\t",
Valid example for mode 2
if (a) {
  b=c;
  function(d) {
    e=f;
  }
}
Invalid example for mode 2
if (a) {
   b=c;
function(d) {
       e=f;
}
}
Valid example for mode "\t"
if (a) {
    b=c;
    function(d) {
        e=f;
    }
}
Invalid example for mode "\t"
if (a) {
     b=c;
function(d) {
           e=f;
 }
}

disallowMixedSpacesAndTabs

Requires lines to not contain both spaces and tabs consecutively, or spaces after tabs only for alignment if "smart"

Type: Boolean or String

Values: true or "smart"

JSHint: smarttabs

Example

"disallowMixedSpacesAndTabs": true
Valid example for mode true
\tvar foo = "blah blah";
\s\s\s\svar foo = "blah blah";
\t/**
\t\s*
\t\s*/ //a single space to align the star in a multi-line comment is allowed
Invalid example for mode true
\t\svar foo = "blah blah";
\s\tsvar foo = "blah blah";
Valid example for mode "smart"
\tvar foo = "blah blah";
\t\svar foo = "blah blah";
\s\s\s\svar foo = "blah blah";
\t/**
\t\s*
\t\s*/ //a single space to align the star in a multi-line comment is allowed
Invalid example for mode "smart"
\s\tsvar foo = "blah blah";

disallowTrailingWhitespace

Requires all lines to end on a non-whitespace character

Type: Boolean

Values: true

JSHint: trailing

Example

"disallowTrailingWhitespace": true
Valid
var foo = "blah blah";
Invalid
var foo = "blah blah"; //<-- whitespace character here

disallowKeywordsOnNewLine

Disallows placing keywords on a new line.

Type: Array

Values: Array of quoted keywords

Example

"disallowKeywordsOnNewLine": ["else"]
Valid
if (x < 0) {
    x++;
} else {
    x--;
}
Invalid
if (x < 0) {
    x++;
}
else {
    x--;
}

requireKeywordsOnNewLine

Requires placing keywords on a new line.

Type: Array

Values: Array of quoted keywords

Example

"requireKeywordsOnNewLine": ["else"]
Valid
if (x < 0) {
    x++;
}
else {
    x--;
}
Invalid
if (x < 0) {
    x++;
} else {
    x--;
}

requireLineFeedAtFileEnd

Requires placing line feed at file end.

Type: Boolean

Values: true

Example

"requireLineFeedAtFileEnd": true

maximumLineLength

Requires all lines to be at most the number of characters specified

Type: Integer

Values: A positive integer

JSHint: maxlen

Example

"maximumLineLength": 40
Valid
var aLineOf40Chars = 123456789012345678;
Invalid
var aLineOf41Chars = 1234567890123456789;

requireCapitalizedConstructors

Requires constructors to be capitalized (except for this)

Type: Boolean

Values: true

JSHint: newcap

Example

"requireCapitalizedConstructors": true
Valid
var a = new B();
var c = new this();
Invalid
var d = new e();

safeContextKeyword

Option to check var that = this expressions

Type: 'Array' or String

Values: String value used for context local declaration

Example

"safeContextKeyword": [ "that" ]
Valid
var that = this;
Invalid
var _this = this;

requireDotNotation

Requires member expressions to use dot notation when possible

Type: Boolean

Values: true

JSHint: sub

Example

"requireDotNotation": true
Valid
var a = b[c];
var a = b.c;
var a = b[c.d];
var a = b[1];
var a = b['while']; //reserved word
Invalid
var a = b['c'];

validateJSDoc

Enables JSDoc validation.

Type: Object

Values:

  • "checkParamNames" ensures param names in jsdoc and in function declaration are equal
  • "requireParamTypes" ensures params in jsdoc contains type
  • "checkRedundantParams" reports redundant params in jsdoc

Example

"validateJSDoc": {
    "checkParamNames": true,
    "checkRedundantParams": true,
    "requireParamTypes": true
}
Valid
/**
 * Adds style error to the list
 *
 * @param {String} message
 * @param {Number|Object} line
 * @param {Number} [column]
 */
add: function(message, line, column) {
}
Invalid
/**
 * Adds style error to the list
 *
 * @param {String} message
 * @param {Number|Object} line
 * @param {Number} [column]
 */
add: function() {
}

excludeFiles

Disables style checking for specified paths.

Type: Array

Values: Array of file matching patterns

Example

"excludeFiles": ["node_modules/**"]

additionalRules

Path to load additional rules

Type: Array

Values: Array of file matching patterns

Example

"additionalRules": ["project-rules/*.js"]

preset

Extends defined rules with preset rules.

Type: String

Values: "jquery"

Example

"preset": "jquery"

If you want specifically disable preset rule assign it to null

"preset": "jquery",
requireCurlyBraces: null

Browser Usage

File jscs-browser.js contains browser-compatible version of jscs.

Download and include jscs-browser.js into your page.

<script type="text/javascript" src="jscs-browser.js"></script>
<script type="text/javascript">
var checker = new JscsStringChecker();
checker.registerDefaultRules();
checker.configure({disallowMultipleVarDecl: true});
var errors = checker.checkString('var x, y = 1;');
errors.getErrorList().forEach(function(error) {
    console.log(errors.explainError(error));
});
</script>
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