How Do I Enumerate and Filter JavaScript Object Properties?

Enumerate Properties of JavaScript Objects

In JavaScript, objects are used to store data as key-value pairs. To retrieve the properties of an object, the for…in loop can be utilized.

Basic Enumeration

const myObject = {
  name: 'Alice',
  age: 25,
  occupation: 'Software Engineer'
};

for (const propertyName in myObject) {
  console.log(propertyName); // Prints: name, age, occupation
  console.log(myObject[propertyName]); // Prints: Alice, 25, Software Engineer
}

Filtering Inherited Properties

By default, the for…in loop also iterates over inherited properties. To filter out inherited properties, the hasOwnProperty() method can be used.

for (const propertyName in myObject) {
  if (myObject.hasOwnProperty(propertyName)) {
    console.log(propertyName); // Prints: name, age, occupation
    console.log(myObject[propertyName]); // Prints: Alice, 25, Software Engineer
  }
}

Considerations

• Private variables are not accessible using the above methods.
• If properties are added or modified dynamically, the results of the enumeration may change.
• It's important to consider the purpose of the enumeration before filtering inherited properties.

The above is the detailed content of How Do I Enumerate and Filter JavaScript Object Properties?. For more information, please follow other related articles on the PHP Chinese website!