Enforce minimum and maximum identifier lengths
Very short identifier names like e, x, _t or very long ones like hashGeneratorResultOutputContainerObject can make code harder to read and potentially less maintainable. To prevent this, one may enforce a minimum and/or maximum identifier length.
var x = 5; // too short; difficult to understand its purpose without context
This rule enforces a minimum and/or maximum identifier length convention.
This rule counts graphemes instead of using String length.
Examples of incorrect code for this rule with the default options:
/*eslint id-length: "error"*/ // default is minimum 2-chars ({ "min": 2 })
/*eslint-env es6*/
var x = 5;
obj.e = document.body;
var foo = function (e) { };
try {
dangerousStuff();
} catch (e) {
// ignore as many do
}
var myObj = { a: 1 };
(a) => { a * a };
class x { }
class Foo { x() {} }
class Foo { #x() {} }
class Foo { x = 1 }
class Foo { #x = 1 }
function foo(...x) { }
function foo([x]) { }
var [x] = arr;
var { prop: [x]} = {};
function foo({x}) { }
var { x } = {};
var { prop: a} = {};
({ prop: obj.x } = {});
Examples of correct code for this rule with the default options:
/*eslint id-length: "error"*/ // default is minimum 2-chars ({ "min": 2 })
/*eslint-env es6*/
var num = 5;
function _f() { return 42; }
function _func() { return 42; }
obj.el = document.body;
var foo = function (evt) { /* do stuff */ };
try {
dangerousStuff();
} catch (error) {
// ignore as many do
}
var myObj = { apple: 1 };
(num) => { num * num };
function foo(num = 0) { }
class MyClass { }
class Foo { method() {} }
class Foo { #method() {} }
class Foo { field = 1 }
class Foo { #field = 1 }
function foo(...args) { }
function foo([longName]) { }
var { prop } = {};
var { prop: [longName] } = {};
var [longName] = arr;
function foo({ prop }) { }
function foo({ a: prop }) { }
var { prop } = {};
var { a: prop } = {};
({ prop: obj.longName } = {});
var data = { "x": 1 }; // excused because of quotes
data["y"] = 3; // excused because of calculated property access
This rule has an object option:
"min" (default: 2) enforces a minimum identifier length"max" (default: Infinity) enforces a maximum identifier length"properties": always (default) enforces identifier length convention for property names"properties": never ignores identifier length convention for property names"exceptions" allows an array of specified identifier names"exceptionPatterns" array of strings representing regular expression patterns, allows identifiers that match any of the patterns.Examples of incorrect code for this rule with the { "min": 4 } option:
/*eslint id-length: ["error", { "min": 4 }]*/
/*eslint-env es6*/
var val = 5;
obj.e = document.body;
function foo (e) { };
try {
dangerousStuff();
} catch (e) {
// ignore as many do
}
var myObj = { a: 1 };
(val) => { val * val };
class x { }
class Foo { x() {} }
function foo(...x) { }
var { x } = {};
var { prop: a} = {};
var [x] = arr;
var { prop: [x]} = {};
({ prop: obj.x } = {});
Examples of correct code for this rule with the { "min": 4 } option:
/*eslint id-length: ["error", { "min": 4 }]*/
/*eslint-env es6*/
var value = 5;
function func() { return 42; }
obj.element = document.body;
var foobar = function (event) { /* do stuff */ };
try {
dangerousStuff();
} catch (error) {
// ignore as many do
}
var myObj = { apple: 1 };
(value) => { value * value };
function foobar(value = 0) { }
class MyClass { }
class Foobar { method() {} }
function foobar(...args) { }
var { prop } = {};
var [longName] = foo;
var { a: [prop] } = {};
var { a: longName } = {};
({ prop: obj.name } = {});
var data = { "x": 1 }; // excused because of quotes
data["y"] = 3; // excused because of calculated property access
Examples of incorrect code for this rule with the { "max": 10 } option:
/*eslint id-length: ["error", { "max": 10 }]*/
/*eslint-env es6*/
var reallyLongVarName = 5;
function reallyLongFuncName() { return 42; }
obj.reallyLongPropName = document.body;
var foo = function (reallyLongArgName) { /* do stuff */ };
try {
dangerousStuff();
} catch (reallyLongErrorName) {
// ignore as many do
}
(reallyLongArgName) => { return !reallyLongArgName; };
var [reallyLongFirstElementName] = arr;
Examples of correct code for this rule with the { "max": 10 } option:
/*eslint id-length: ["error", { "max": 10 }]*/
/*eslint-env es6*/
var varName = 5;
function funcName() { return 42; }
obj.propName = document.body;
var foo = function (arg) { /* do stuff */ };
try {
dangerousStuff();
} catch (error) {
// ignore as many do
}
(arg) => { return !arg; };
var [first] = arr;
Examples of correct code for this rule with the { "properties": "never" } option:
/*eslint id-length: ["error", { "properties": "never" }]*/
/*eslint-env es6*/
var myObj = { a: 1 };
({ a: obj.x.y.z } = {});
({ prop: obj.i } = {});
Examples of additional correct code for this rule with the { "exceptions": ["x"] } option:
/*eslint id-length: ["error", { "exceptions": ["x"] }]*/
/*eslint-env es6*/
var x = 5;
function x() { return 42; }
obj.x = document.body;
var foo = function (x) { /* do stuff */ };
try {
dangerousStuff();
} catch (x) {
// ignore as many do
}
(x) => { return x * x; };
var [x] = arr;
const { x } = foo;
const { a: x } = foo;
Examples of additional correct code for this rule with the { "exceptionPatterns": ["E|S", "[x-z]"] } option:
/*eslint id-length: ["error", { "exceptionPatterns": ["E|S", "[x-z]"] }]*/
/*eslint-env es6*/
var E = 5;
function S() { return 42; }
obj.x = document.body;
var foo = function (x) { /* do stuff */ };
try {
dangerousStuff();
} catch (x) {
// ignore as many do
}
(y) => {return y * y};
var [E] = arr;
const { y } = foo;
const { a: z } = foo;
This rule was introduced in ESLint v1.0.0.
© OpenJS Foundation and other contributors
Licensed under the MIT License.
https://eslint.org/docs/latest/rules/id-length