enforce a maximum number of classes per file (max-classes-per-file)

Files containing multiple classes can often result in a less navigable and poorly structured codebase. Best practice is to keep each file limited to a single responsibility.

Rule Details

This rule enforces that each file may contain only a particular number of classes and no more.

Examples of incorrect code for this rule:

/*eslint max-classes-per-file: "error"*/

class Foo {}
class Bar {}

Examples of correct code for this rule:

/*eslint max-classes-per-file: "error"*/

class Foo {}

Options

This rule may be configured with either an object or a number.

If the option is an object, it may contain one or both of:

• ignoreExpressions: a boolean option (defaulted to false) to ignore class expressions.
• max: a numeric option (defaulted to 1) to specify the maximum number of classes.

For example:

{
    "max-classes-per-file": ["error", 1]
}

{
    "max-classes-per-file": [
        "error",
        { "ignoreExpressions": true, "max": 2 }
    ]
}

Examples of correct code for this rule with the max option set to 2:

/* eslint max-classes-per-file: ["error", 2] */

class Foo {}
class Bar {}

Examples of correct code for this rule with the ignoreExpressions option set to true:

/* eslint max-classes-per-file: ["error", { ignoreExpressions: true }] */

class VisitorFactory {
    forDescriptor(descriptor) {
        return class {
            visit(node) {
                return `Visiting ${descriptor}.`;
            }
        };
    }
}

Version

This rule was introduced in ESLint 5.0.0-alpha.3.

Resources

• Rule source
• Documentation source