How to Properly Check if a JavaScript Object Property is Undefined

When writing JavaScript code, it is important to know the correct way to check if an object property is undefined. The most reliable method to accomplish this is by using the typeof operator. Let me guide you through the process with this easy explanation.

To check if an object property is undefined, you simply utilize the typeof operator. This operator returns a string that represents the type of the given operand. It should be noted that the typeof operator does not require parentheses and can be used with any value you want to check.

For example, let’s consider the following scenarios:

const list = [];
const count = 2;

typeof list; // "object"
typeof count; // "number"
typeof "test"; // "string"

typeof color; // "undefined"

In the above code snippet, the typeof operator is used to check the types of different values. As you can see, it successfully determines the types of the given operands. When the value is not defined, the typeof operator returns the string 'undefined'.

Now, let’s imagine you have a car object with the following structure:

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const car = {
  model: 'Fiesta'
};

If you want to check if the color property is defined on this object, you can do so by using the following code:

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if (typeof car.color === 'undefined') {
  // The color is undefined
}

By using the typeof operator, you can accurately check if an object property is undefined in JavaScript.

tags: [“JavaScript”, “object property”, “undefined”, “typeof operator”]