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< Orion
Revision as of 12:03, 18 November 2013 by (Talk | contribs) (Nice to have)

Orion 5.0 will replace our current [JSLint validator with ESLint. This page captures ongoing issues.


Here's a table showing the equivalent validation rules in JSLint and ESLint. Rules that JSLint does not support are marked as Unsupported.

ESLint rule JSLint option JSLint message Details
block-scoped-var Always on '{variable}' is already defined.
  • Occurs when a function-scoped variable is treated as if it was block scoped.
  • ESLint calls this error '{variable} used outside of binding context.'
brace-style Unsupported
camelcase Unsupported
complexity Unsupported
consistent-this Unsupported
curly Always on
  • Statement body should be inside '{ }' braces. (Orion)
  • Expected '{'. (Regular JSLint)
dot-notation sub {a} is better written in dot notation.
eqeqeq eqeqeq or eqeq
  • Expected '===' and saw '=='.
  • Expected '!==' and saw '!='.
  • Newer versions of JSLint call this option eqeqeq.
  • Orion's version calls it eqeq, and inverts the flag's value.
guard-for-in forin The body of a for in should be wrapped in an if statement to filter unwanted properties from the prototype.
max-depth Unsupported Enforces max depth of nested blocks within a function.
max-len maxlen Line too long. Enforces a maximum line length.
max-params Unsupported
max-statements Unsupported
new-cap newcap A constructor name should start with an uppercase letter.
new-parens Always on Missing '()' invoking a constructor. Flags new Whatever
no-alert devel '{alert, confirm, prompt}' is not defined.
no-bitwise bitwise Unexpected use of '{operator}'. JSLint disallows bitwise ops by default.
no-caller Unsupported Flags references to arguments.callee and arguments.caller.
no-catch-shadow Always on '{a}' is already defined.
  • Flags a catch clause's variable that shadows a variable declared in an outer scope. (In IE8 this [ causes the outer variable to be overwritten]).
no-comma-dangle Always on Unexpected comma. Flags trailing commas in object literals.
no-cond-assign Unsupported Flags assignment in an if/while/do..while/for condition.
no-console devel
no-control-regex Unsupported Flags control characters (U+0000–U+001F and U+007F) within the source argument to the RegExp constructor.
no-debugger debug All 'debugger' statements should be removed.
no-delete-var Always on Expected '.' and instead saw ';'. Flags an attempt to delete a local variable.
no-div-regex Always on A regular expression literal can be confused with '/='. Flags a regex literal starting with /=
no-dupe-keys Always on Duplicate key '{a}'. Flags object literals that contain the same key more than once.
no-else-return Unsupported Flags an else appearing after an if that contains a return.
no-empty-class Always on Empty class. Flags an empty character class [] within a regular expression.
no-empty-label Always on Label '{a}' on statement. Flags a labeled statement that is not a switch, for, or while.
no-empty Unsupported Flags an empty block like if (something) { }.
no-eq-null Always on Use '===' to compare with 'null'. JSLint produces a similar warning when comparing against undefined.
no-eval evil eval is evil.
no-ex-assign Always on Do not assign to the exception parameter.
no-extra-semi Always on Unnecessary semicolon.
no-fallthrough Unsupported Flags a fallthrough case within a switch statement, unless it is explicitly commented.
no-floating-decimal Always on A {leading, trailing} decimal point can be confused with a dot: '{n}'. Flags numeric literals that have a leading or trailing decimal point.
no-func-assign Unsupported Flags assignment to a variable that's already bound to a FunctionExpression.
no-global-strict Unsupported Flags "use strict" applied to the entire Program.
no-implied-eval Always on Implied eval is evil. Pass a function instead of a string. Flags calls to the string-argument form of setTimeout and setInterval, which implicitly perform eval.
no-iterator Always on Reserved name '__iterator__'. Flags use of __iterator__ as an identifier name or property key.
no-label-var Always on '{label}' is already defined. Flags labels that collide with an identifier.
no-loop-func Always on Don't make functions within a loop.
no-mixed-requires Flags Node.js require()s that mix different types of requires (core, module, file, computed).
no-multi-str Flags use of ES5 multiline string literals.
no-native-reassign Always on
  • Read only.
  • Bad assignment. (if assigning to undefined)
Flags an attempt to reassign a native object like Math, Array, undefined, etc.
no-negated-in-lhs Unsupported
  • Flags a unary ! operator applied to the LHS of an in statement, which negates the LHS, not the in.
  • Eg. (!"key" in {key: 1}) (which always evaluates to false), will be flagged.
no-new-array Always on Use the array literal notation []. Flags new Array().
no-new-func Always on The Function constructor is eval.
no-new-object Always on Use the object literal notation {}. Flags new Object().
no-new-wrappers Do not use {String, Number, Boolean, Math, JSON} as a constructor. Flags new applied to any of those.
no-new Always on Do not use 'new' for side effects. Flags uses of new operator in an expression that is not assigned to anything.
no-obj-calls Partial support Math is not a function..
  • Flags attempts to call object properties of the global object (Math, JSON) as a function, like Math().
  • JSLint warns only on Math().
no-octal-escape Always on Bad escapement. Flags octal escapes in strings, for example var x = "Copyright \251";
no-octal Always on Don't use extra leading zeros '{n}'. Flags number literals that begin with leading 0s, which indicate a (probably accidental) octal literal.
no-plusplus plusplus
  • Unexpected use of '++'
  • Unexpected use of '--'
no-proto Always on
  • Reserved name '__proto__'. (if used as an identifier)
  • Stupid key '{a}'. (if used as a key)
Treated as a fatal parse error in JSLint.
no-redeclare Always on '{a}' is already defined. Usually results from having two for loops in the same function that share a loop variable declaration like var i=....
no-return-assign Unsupported
  • Prevents assignment in a return statement.
  • Unsupported by JSLint, although JSLint does require parens around a return-assignment, eg: return (x = 2);
no-script-url Always on Script URL.
  • Flags string literals beginning with javascript:. (Script URLs are a form of eval.)
  • Fatal parse error in JSLint.
no-self-compare Unsupported Flags comparisons where the left- and right-hand sides are the same.
no-shadow Unsupported Flags variables that have the same name as a variable declared in an outer scope.
no-sync stupid Unexpected sync method: '{a}'.
  • Flags Node.js's synchronous I/O methods.
  • The stupid option is supported only in newer versions of JSLint (not Orion's).
no-ternary Unsupported Flags any use of the ternary operator cond ? thenExpr : elseExpr
no-undef-init Always on It is not necessary to initialize '{variable}' to 'undefined'.
no-undef undef '{variable}' is not defined.
  • Flags references to a global variable that is not listed in a /*global*/ or /*globals*/ block.
  • Predefined environments (eg. node, browser) can be set in the /*jslint */ block.
no-underscore-dangle nomen Dangling '_'
no-unreachable Always on Unreachable '{statement}' after '{control flow statement}'. Flags statements that occur after a return, throw, etc.
no-unused-expressions Always on Expected an assignment or function call and instead saw an expression. Flags expressions that appear in a statement context and don't cause side effects.
no-unused-vars Always on Function declares unused variable '{a}'. (Orion) Newer JSlint versions have an unparam option which works similarly.
no-use-before-define Always on '{a}' was used before it was defined.
no-with Always on Expected an identifier and instead saw 'with'. Treated as fatal parse error in JSLint.
no-wrap-func Always on Do not wrap function literals in parens unless they are to be immediately invoked. Flags a parenthesized function literal that is not immediately invoked, eg. (function fun(){})
one-var onevar Too many var statements. Allows only 1 var statement per function.
quote-props Unsupported Requires object literal keys to be quoted with " or '.
quotes Unsupported Flags any use of single or double quote marks, depending on setting.
radix Always on Missing radix parameter. Affects parseInt().
regex-spaces Always on Spaces are hard to count. Use {n}.
semi Always on Missing semicolon.
strict strict Flags any code that lacks the "use strict" pragma.
unnecessary-strict Unsupported Flags "use strict" on a function when the entire Program is already in strict mode.
use-isnan Always on Use the isNaN function to compare with NaN.
wrap-iife immed
  • Wrap the entire immediate function invocation in parens.
  • Move the invocation into the parens that contain the function.
Flags missing parens on immediately-invoked functions, eg. function(){ console.log('hi'); }();
wrap-regex Always on Wrap the /regexp/ literal in parens to disambiguate the slash operator.

Rule priority

Here are the rules we want, grouped by priority:


  • no-undef
  • eqeqeq
  • block-scoped-var
  • no-redeclare


  • guard-for-in
  • no-unused-vars
  • no-dupe-keys
  • no-octal
  • radix
  • wrap-iife

Nice to have

  • dot-notation
  • new-cap
  • new-parens
  • no-caller
  • no-comma-dangle
  • no-implied-eval
  • no-new-array
  • no-new-object
  • no-undef-init
  • no-unused-expressions
  • no-wrap-func
  • semi

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