Function isObject
has 40 lines of code (exceeds 25 allowed). Consider refactoring. Open
export default function isObject(...args) {
const validator = isPlainObject(args[0]) ? undefined : args[0];
const { unmanaged = false } = (isPlainObject(args[0]) ? args[0] : args[1]) || {};
return (input, info) => {
Avoid too many return
statements within this function. Open
return {
key: `.${key}${result.key}`,
value: result.value,
message: result.message,
};
Avoid too many return
statements within this function. Open
return {
key: `.${key}`,
value: input[key],
message: result,
};
Avoid too many return
statements within this function. Open
return true;
iterators/generators require regenerator-runtime, which is too heavyweight for this guide to allow them. Separately, loops should be avoided in favor of array iterations. Open
for (const key of Object.keys(input)) {
- Read upRead up
- Exclude checks
disallow specified syntax (no-restricted-syntax)
JavaScript has a lot of language features, and not everyone likes all of them. As a result, some projects choose to disallow the use of certain language features altogether. For instance, you might decide to disallow the use of try-catch
or class
, or you might decide to disallow the use of the in
operator.
Rather than creating separate rules for every language feature you want to turn off, this rule allows you to configure the syntax elements you want to restrict use of. These elements are represented by their ESTree node types. For example, a function declaration is represented by FunctionDeclaration
and the with
statement is represented by WithStatement
. You may find the full list of AST node names you can use on GitHub and use the online parser to see what type of nodes your code consists of.
You can also specify [AST selectors](../developer-guide/selectors) to restrict, allowing much more precise control over syntax patterns.
Rule Details
This rule disallows specified (that is, user-defined) syntax.
Options
This rule takes a list of strings, where each string is an AST selector:
{
"rules": {
"no-restricted-syntax": ["error", "FunctionExpression", "WithStatement", "BinaryExpression[operator='in']"]
}
}
Alternatively, the rule also accepts objects, where the selector and an optional custom message are specified:
{
"rules": {
"no-restricted-syntax": [
"error",
{
"selector": "FunctionExpression",
"message": "Function expressions are not allowed."
},
{
"selector": "CallExpression[callee.name='setTimeout'][arguments.length!=2]",
"message": "setTimeout must always be invoked with two arguments."
}
]
}
}
If a custom message is specified with the message
property, ESLint will use that message when reporting occurrences of the syntax specified in the selector
property.
The string and object formats can be freely mixed in the configuration as needed.
Examples of incorrect code for this rule with the "FunctionExpression", "WithStatement", BinaryExpression[operator='in']
options:
/* eslint no-restricted-syntax: ["error", "FunctionExpression", "WithStatement", "BinaryExpression[operator='in']"] */
with (me) {
dontMess();
}
var doSomething = function () {};
foo in bar;
Examples of correct code for this rule with the "FunctionExpression", "WithStatement", BinaryExpression[operator='in']
options:
/* eslint no-restricted-syntax: ["error", "FunctionExpression", "WithStatement", "BinaryExpression[operator='in']"] */
me.dontMess();
function doSomething() {};
foo instanceof bar;
When Not To Use It
If you don't want to restrict your code from using any JavaScript features or syntax, you should not use this rule.
Related Rules
- [no-alert](no-alert.md)
- [no-console](no-console.md)
- [no-debugger](no-debugger.md)
- [no-restricted-properties](no-restricted-properties.md) Source: http://eslint.org/docs/rules/
Unexpected parentheses around single function argument having a body with no curly braces Open
wrapper: (wrap) => `Object(${wrap})`,
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- Exclude checks
Require parens in arrow function arguments (arrow-parens)
Arrow functions can omit parentheses when they have exactly one parameter. In all other cases the parameter(s) must be wrapped in parentheses. This rule enforces the consistent use of parentheses in arrow functions.
Rule Details
This rule enforces parentheses around arrow function parameters regardless of arity. For example:
/*eslint-env es6*/
// Bad
a => {}
// Good
(a) => {}
Following this style will help you find arrow functions (=>
) which may be mistakenly included in a condition
when a comparison such as >=
was the intent.
/*eslint-env es6*/
// Bad
if (a => 2) {
}
// Good
if (a >= 2) {
}
The rule can also be configured to discourage the use of parens when they are not required:
/*eslint-env es6*/
// Bad
(a) => {}
// Good
a => {}
Options
This rule has a string option and an object one.
String options are:
-
"always"
(default) requires parens around arguments in all cases. -
"as-needed"
allows omitting parens when there is only one argument.
Object properties for variants of the "as-needed"
option:
-
"requireForBlockBody": true
modifies the as-needed rule in order to require parens if the function body is in an instructions block (surrounded by braces).
always
Examples of incorrect code for this rule with the default "always"
option:
/*eslint arrow-parens: ["error", "always"]*/
/*eslint-env es6*/
a => {};
a => a;
a => {'\n'};
a.then(foo => {});
a.then(foo => a);
a(foo => { if (true) {} });
Examples of correct code for this rule with the default "always"
option:
/*eslint arrow-parens: ["error", "always"]*/
/*eslint-env es6*/
() => {};
(a) => {};
(a) => a;
(a) => {'\n'}
a.then((foo) => {});
a.then((foo) => { if (true) {} });
If Statements
One of benefits of this option is that it prevents the incorrect use of arrow functions in conditionals:
/*eslint-env es6*/
var a = 1;
var b = 2;
// ...
if (a => b) {
console.log('bigger');
} else {
console.log('smaller');
}
// outputs 'bigger', not smaller as expected
The contents of the if
statement is an arrow function, not a comparison.
If the arrow function is intentional, it should be wrapped in parens to remove ambiguity.
/*eslint-env es6*/
var a = 1;
var b = 0;
// ...
if ((a) => b) {
console.log('truthy value returned');
} else {
console.log('falsey value returned');
}
// outputs 'truthy value returned'
The following is another example of this behavior:
/*eslint-env es6*/
var a = 1, b = 2, c = 3, d = 4;
var f = a => b ? c: d;
// f = ?
f
is an arrow function which takes a
as an argument and returns the result of b ? c: d
.
This should be rewritten like so:
/*eslint-env es6*/
var a = 1, b = 2, c = 3, d = 4;
var f = (a) => b ? c: d;
as-needed
Examples of incorrect code for this rule with the "as-needed"
option:
/*eslint arrow-parens: ["error", "as-needed"]*/
/*eslint-env es6*/
(a) => {};
(a) => a;
(a) => {'\n'};
a.then((foo) => {});
a.then((foo) => a);
a((foo) => { if (true) {} });
Examples of correct code for this rule with the "as-needed"
option:
/*eslint arrow-parens: ["error", "as-needed"]*/
/*eslint-env es6*/
() => {};
a => {};
a => a;
a => {'\n'};
a.then(foo => {});
a.then(foo => { if (true) {} });
(a, b, c) => a;
(a = 10) => a;
([a, b]) => a;
({a, b}) => a;
requireForBlockBody
Examples of incorrect code for the { "requireForBlockBody": true }
option:
/*eslint arrow-parens: [2, "as-needed", { "requireForBlockBody": true }]*/
/*eslint-env es6*/
(a) => a;
a => {};
a => {'\n'};
a.map((x) => x * x);
a.map(x => {
return x * x;
});
a.then(foo => {});
Examples of correct code for the { "requireForBlockBody": true }
option:
/*eslint arrow-parens: [2, "as-needed", { "requireForBlockBody": true }]*/
/*eslint-env es6*/
(a) => {};
(a) => {'\n'};
a => ({});
() => {};
a => a;
a.then((foo) => {});
a.then((foo) => { if (true) {} });
a((foo) => { if (true) {} });
(a, b, c) => a;
(a = 10) => a;
([a, b]) => a;
({a, b}) => a;
Further Reading
- The
"as-needed", { "requireForBlockBody": true }
rule is directly inspired by the Airbnb JS Style Guide. Source: http://eslint.org/docs/rules/