eslint/complexity Restriction
What it does
Enforces a maximum cyclomatic complexity in a program, which is the number of linearly independent paths in a program.
Why is this bad?
Having high code complexity reduces code readability. This rule aims to make the code easier to follow by reducing the number of branches in the program.
Examples
Examples of incorrect code for this rule with { "max": 2 }
js
function foo() {
if (foo1) {
return x1; // 1st path
} else if (foo2) {
return x2; // 2nd path
} else {
return x3; // 3rd path
}
}
function bar() {
// there are 2 paths - when bar1 is falsy, and when bar1 is truthy, in which bar1 = bar1 && bar2;
bar1 &&= bar2;
// there are 2 paths - when bar3 is truthy, and when bar3 is falsy, in which bar3 = 4;
bar3 ||= 4;
}
// there are 2 paths - when baz1 is defined, and when baz1 is undefined and is assigned 'a'
function baz(baz1 = "a") {
const { baz2 = "b" } = baz3; // there are 2 additional paths - when baz2 is defined and when baz2 is not
}
function d() {
d1 = d2?.d3?.(); // optional chaining creates 2 paths each - when object is defined and when it is not
}Examples of correct code for this rule with { "max": 2 }
js
// This example is taken directly from ESLint documentation
function foo() {
// this function has complexity = 1
class C {
x = a + b; // this initializer has complexity = 1
y = c || d; // this initializer has complexity = 2
z = e && f; // this initializer has complexity = 2
static p = g || h; // this initializer has complexity = 2
static q = i ? j : k; // this initializer has complexity = 2
static {
// this static block has complexity = 2
if (foo) {
baz = bar;
}
}
static {
// this static block has complexity = 2
qux = baz || quux;
}
}
}Configuration
This rule accepts a configuration object with the following properties:
max
type: integer
default: 20
Maximum amount of cyclomatic complexity
variant
type: "classic" | "modified"
default: "classic"
The cyclomatic complexity variant to use
"classic"
Classic means McCabe cyclomatic complexity
"modified"
Modified means classic cyclomatic complexity but a switch statement increases complexity by 1 irrespective of the number of case statements
How to use
To enable this rule using the config file or in the CLI, you can use:
json
{
"rules": {
"complexity": "error"
}
}bash
oxlint --deny complexity