Have you ever encountered a perplexing ESLint warning that led you down a rabbit hole of unexpected errors? Recently, I found myself in such a scenario involving the hasOwnProperty() property of an object.
In a recent coding, I encountered an ESLint error originating from this seemingly harmless line of code:
console.log(myObject.hasOwnProperty('someProperty'));
But why the sudden flag from ESLint? The revelation occurred when ESLint pointed out an issue with calling hasOwnProperty directly on an object, prompting a much-needed reevaluation of my coding approach.
The solution presented itself in the form of a slightly modified syntax:
// Calling hasOwnProperty using Object.prototype.hasOwnProperty.call
console.log(Object.prototype.hasOwnProperty.call(myObject, 'someProperty'));
Now, why this adjustment? The key lies in the potential pitfalls when an object contains a property named 'hasOwnProperty'. Consider the following scenario:
// An object with a property named 'hasOwnProperty'
const myObject = {
hasOwnProperty: 'I am a property',
};
// Calling hasOwnProperty directly on myObject
// This results in an error because myObject.hasOwnProperty is a string, not a function
console.log(myObject.hasOwnProperty('someProperty')); // Error!
By switching to Object.prototype.hasOwnProperty.call, I ensured that the hasOwnProperty method was invoked from the prototype chain, mitigating any unforeseen errors tied to unconventional object properties. While the chances of encountering such scenarios may be rare, this adjustment not only addresses the ESLint warning but also serves as a robust preventive measure.
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