JavaScript For In Loop
JavaScript For In Loop
In JavaScript, the for…in loop is used to iterate over the properties of an object. Here’s the basic syntax of a for…in loop:
for (variable in object) {
// code to be executed
}
The variable is a variable that represents the current property name being iterated over. The object is the object being iterated over.
Here’s an example of a for…in loop that iterates over the properties of an object:
const person = {
name: "John",
age: 30,
gender: "male"
};
for (let prop in person) {
console.log(`${prop}: ${person[prop]}`);
}
In this example, the for…in loop iterates over the properties of the person object. The prop variable represents the current property name being iterated over. The code inside the loop logs each property name and value to the console.
It’s important to note that the for…in loop should only be used for iterating over the enumerable properties of an object. It does not guarantee any particular order of iteration, so if the order of iteration is important, you should use a different method, such as Object.keys(). Additionally, the for…in loop will also iterate over any properties inherited from the object’s prototype chain. To avoid this, you can use the hasOwnProperty() method to check if the object has the property directly, like this:
for (let prop in person) {
if (person.hasOwnProperty(prop)) {
console.log(`${prop}: ${person[prop]}`);
}
}