no-this-before-super

Disallow this/super before calling super() in constructors

✅

Using the recommended config from @eslint/js in a configuration file enables this rule

In the constructor of derived classes, if this/super are used before super() calls, it raises a reference error.

This rule checks this/super keywords in constructors, then reports those that are before super().

Rule Details

This rule is aimed to flag this/super keywords before super() callings.

Examples

Examples of incorrect code for this rule:

Open in Playground

/*eslint no-this-before-super: "error"*/

class A1 extends B {
    constructor() {
        this.a = 0;
        super();
    }
}

class A2 extends B {
    constructor() {
        this.foo();
        super();
    }
}

class A3 extends B {
    constructor() {
        super.foo();
        super();
    }
}

class A4 extends B {
    constructor() {
        super(this.foo());
    }
}
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Examples of correct code for this rule:

Open in Playground

/*eslint no-this-before-super: "error"*/

class A1 {
    constructor() {
        this.a = 0; // OK, this class doesn't have an `extends` clause.
    }
}

class A2 extends B {
    constructor() {
        super();
        this.a = 0; // OK, this is after `super()`.
    }
}

class A3 extends B {
    foo() {
        this.a = 0; // OK. this is not in a constructor.
    }
}
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When Not To Use It

If you don’t want to be notified about using this/super before super() in constructors, you can safely disable this rule.

Handled by TypeScript

It is safe to disable this rule when using TypeScript because TypeScript's compiler enforces this check.

Version

This rule was introduced in ESLint v0.24.0.

Resources

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