# no-setter-return

Disallow setters to return values.

Setters cannot return values. To be more precise, a setter that returns a value is not treated as an error, but we cannot use the returned value at all. Thus, if you write a setter that will return something, it is most likely either completely unnecessary or a possible error.

Note that return without a value is allowed because it is considered a control flow statement.

This rule checks setters in:

  • Object literals
  • Class declarations and class expressions
  • Property descriptors in Object.create, Object.defineProperty, Object.defineProperties, and Reflect.defineProperty

# Incorrect code examples

let foo = {
    set a(value) {
        this.val = value;
        // The setter always returns a value
        return value;
    }
};

class Foo {
    set a(value) {
        this.val = value;
        // The setter always returns a value
        return this.val;
    }
}

const Bar = class {
    static set a(value) {
        if (value < 0) {
            this.val = 0;
            // The setter returns `0` if the value is negative
            return 0;
        }
        this.val = value;
    }
};

Object.defineProperty(foo, "bar", {
    set(value) {
        if (value < 0) {
            // The setter returns `false` if the value is negative
            return false;
        }
        this.val = value;
    }
});

# Correct code examples

let foo = {
    set a(value) {
        this.val = value;
    }
};

class Foo {
    set a(value) {
        this.val = value;
    }
}

const Bar = class {
    static set a(value) {
        if (value < 0) {
            this.val = 0;
            // Returning without a value is allowed
            return;
        }
        this.val = value;
    }
};

Object.defineProperty(foo, "bar", {
    set(value) {
        if (value < 0) {
            // Throwing an error is also allowed
            throw new Error("Negative value is not allowed.");
        }
        this.val = value;
    }
});
More incorrect examples
let foo = {
    set bar(val) {
        return 42;
    }
};
let bar = {
    set foo(val) {
        if (bar) {
            return 42;
        }
    }
};
let bar = {
    set foo(val) {
        switch (bar) {
            case 5:
            case 6:
            if (bar) {
                return 42;
            }
        }
    }
};
let bar = {
    set foo(val) {
        if (bar) {

        } else {
            return 42;
        }
    }
};
class Foo {
    set bar(val) {
        return 42;
    }
}
let Foo = class {
    set bar(val) {
        return 42;
    }
};
Object.create(null, {
    foo: {
        set(val) {
            return 42;
        }
    }
});
Object.defineProperty(foo, 'bar', {
    set(val) {
        return 42;
    }
});
Object.defineProperties(foo, 'bar', {
    set(val) {
        return 42;
    }
});
Reflect.defineProperties(foo, 'bar', {
    set(val) {
        return 42;
    }
});
More correct examples
({ set foo(val) { return; } })
({ set foo(val) { if (val) { return; } } })
class A { set foo(val) { return; } }
(class { set foo(val) { if (val) { return; } else { return; } return; } })
class A { set foo(val) { try {} catch(e) { return; } } }
Object.defineProperty(foo, 'bar', { set(val) { return; } })

Source (opens new window)

Last Updated: 11/18/2020, 9:36:33 PM