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Explain the difference between a function and a method in JavaScript?
In JavaScript, the terms “function” and “method” are often used interchangeably, but there is a subtle difference between them based on how they are invoked and associated with objects.
A function is a standalone block of code that performs a specific task. It can be defined globally or within the scope of another function or block. Functions can accept arguments, execute statements, and return a value.
On the other hand, a method is a function that is associated with an object. It is defined as a property of an object and is accessed using the object’s reference. Methods are typically used to perform actions or operations related to the object they belong to.
Here are some key differences between functions and methods in JavaScript:
Invocation: Functions can be invoked independently by calling their name, while methods are invoked using an object reference, followed by the dot notation and the method name.
Context: Functions have no inherent context and can operate independently. Methods, on the other hand, are bound to an object and can access the object’s properties and other methods using the
thiskeyword.Relationship to an object: Functions are not tied to any specific object and can be used globally. Methods, however, are associated with a specific object and can access and manipulate that object’s data.
Here’s an example to illustrate the difference:
// Function
function calculateArea(radius) {
return Math.PI * radius * radius;
}
console.log(calculateArea(5)); // Output: 78.53981633974483
// Method
const circle = {
radius: 5,
calculateArea: function() {
return Math.PI * this.radius * this.radius;
}
};
console.log(circle.calculateArea()); // Output: 78.53981633974483
In the example above, calculateArea is a standalone function that calculates the area of a circle. It can be invoked directly using its name. On the other hand, the calculateArea method is associated with the circle object, accessed using circle.calculateArea(). It uses the object’s properties (this.radius) to perform the calculation.
In summary, while both functions and methods are blocks of code that perform a specific task, methods are specifically associated with an object and have access to the object’s properties and other methods using the this keyword.
Provide examples of using default parameters in a function in JavaScript?
Default parameters allow you to specify default values for function parameters. If no argument is provided for a parameter or if the argument is undefined, the default value is used instead. Here are some examples of using default parameters in JavaScript:
Example 1: Setting a default value for a single parameter
function greet(name = 'friend') {
console.log(`Hello, ${name}!`);
}
greet(); // Output: Hello, friend!
greet('John'); // Output: Hello, John!
In the example above, the greet function has a single parameter name with a default value of 'friend'. If no argument is passed or if the argument is undefined, the default value 'friend' is used.
Example 2: Using default parameters with multiple parameters
function multiply(a, b = 1) {
return a * b;
}
console.log(multiply(5)); // Output: 5
console.log(multiply(3, 4)); // Output: 12
In this example, the multiply function has two parameters: a and b. The b parameter has a default value of 1. If the b argument is not provided or is undefined, the default value of 1 is used.
Example 3: Using expressions as default parameter values
function repeatString(string, count = string.length) {
return string.repeat(count);
}
console.log(repeatString('Hello')); // Output: HelloHelloHelloHelloHello
console.log(repeatString('Hi', 3)); // Output: HiHiHi
In this example, the repeatString function has two parameters: string and count. The default value of count is set to the length of the string parameter. If the count argument is not provided, the default value will be the length of the string.
Default parameters provide a convenient way to define fallback values in functions and make the function calls more flexible by allowing some arguments to be optional.
Explain the concept of higher-order functions in JavaScript?
In JavaScript, higher-order functions are functions that can take other functions as arguments or return functions as their results. This concept is derived from functional programming paradigms and provides a powerful way to compose and manipulate functions.
Here are some key aspects of higher-order functions:
Accepting a function as an argument: A higher-order function can take another function as an argument. The function being passed is commonly referred to as a “callback” function. The higher-order function can then invoke the callback function at a later point or use it to perform some specific task.
Returning a function: A higher-order function can also return a function as its result. This allows for the creation of specialized or customized functions based on the input arguments or conditions within the higher-order function.
Higher-order functions are powerful because they enable code abstraction, modularization, and the implementation of reusable logic. They allow you to separate concerns, improve code organization, and create more expressive and flexible code structures.
Here’s an example to illustrate the concept:
function higherOrderFunction(callback) {
console.log('Performing some operations before invoking the callback...');
callback();
console.log('Operations after invoking the callback.');
}
function callbackFunction() {
console.log('This is the callback function.');
}
higherOrderFunction(callbackFunction);
In the code above, higherOrderFunction is a higher-order function that takes callbackFunction as an argument. When higherOrderFunction is called, it executes some operations before invoking the callback and then performs operations after invoking the callback. The callbackFunction is passed as an argument and is invoked within the higher-order function.
Higher-order functions are widely used in JavaScript, especially in scenarios such as event handling, asynchronous operations, functional programming patterns like map, filter, and reduce, and in creating reusable utility functions.
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