When do I get this error?

The "'hasOwnProperty' is a really bad name" error is thrown when JSHint encounters an assignment to an object property with the identifier hasOwnProperty. This applies to both object literals and to normal assignment statements. In the following example we define an object with a property called hasOwnProperty:

var demo = {
    hasOwnProperty: 1
};

Why do I get this error?

This error is raised to highlight confusing code that could cause problems in the future. Your code may run as expected but it's likely to cause issues with maintenance and be confusing to other developers.

Most objects in JavaScript have access (via inheritance from Object.prototype) to the hasOwnProperty method which is used to check whether a given property is defined on a given object. This method is commonly used within for...in loops to ensure only enumerable properties of the object in question are handled, and not enumerable properties of objects further down its prototype chain. See the somewhat related "The body of a for in should be wrapped in an if statement to filter unwanted properties from the prototype" error for more details:

/*global doSomething */
var me = {
    name: "James",
    age: 23
};

for (var prop in me) {
    if (me.hasOwnProperty(prop)) {
        doSomething(prop);
    }
}

In that example, were you to add a property hasOwnProperty: 1 to me, the guard in the for...in loop would fail with an error telling you that hasOwnProperty is not a function. If the value of your custom hasOwnProperty is a function then it will be invoked and the code may work but would be very misleading to anyone else reading.

The solution to this error is to simply not use hasOwnProperty as a property identifer. If you are concerned that the value of hasOwnProperty is no longer the native function you may want to call the native function in the context of your object in for...in loop guards:

/*global doSomething */
var me = {
    name: "James",
    age: 23,
    hasOwnProperty: 1 // This would cause the previous example to fail
};

for (var prop in me) {
    if (Object.hasOwnProperty.call(me, prop)) { // Use the real hasOwnProperty
        doSomething(prop);
    }
}

In JSHint 1.0.0 and above you have the ability to ignore any warning with a special option syntax. The identifier of this warning is W001. This means you can tell JSHint to not issue this warning with the /*jshint -W001 */ directive.