JavaScript Functions - Important Points
JavaScript functions are an essential part of any JavaScript program. They allow you to group code together, give it a name, and reuse it throughout your code. here, we will cover the important points that beginners need to know about JavaScript functions.
How to Define a function in JavaScript
First of all, a JavaScript function is a block of code that performs a specific task. You can define a function using the "function" keyword, followed by the name of the function, and a set of parentheses. The code you want to execute is placed between curly braces.
For example, here is a simple function that adds two numbers together:
function addNumbers(num1, num2) {
return num1 + num2;
}
In this function, "num1" and "num2" are the parameters, which are placeholders for the values that will be passed into the function when it is called. The "return" keyword indicates what value the function should output when it is called.
How to Call a function in JavaScript
To call a function, you simply use the name of the function followed by a set of parentheses, with any arguments you want to pass in.
let result = addNumbers(2, 3);
console.log(result); // Outputs 5
In this example, we call the "addNumbers" function with the values 2 and 3, and store the result in the "result" variable. We then output the value of the "result" variable to the console.
Functions can also be used to create objects, which are instances of a class. In JavaScript, classes are defined using a constructor function, which is a special type of function that is used to create objects.
function Person(name, age) {
this.name = name;
this.age = age;
}
let person1 = new Person("John", 30);
let person2 = new Person("Mary", 25);
console.log(person1.name); // Outputs "John"
console.log(person2.age); // Outputs 25
In this example, we define a constructor function called "Person", which takes two parameters: "name" and "age". The "this" keyword is used to assign these parameters to properties of the object being created. We then create two instances of the "Person" class using the "new" keyword, and output their properties to the console.
JavaScript also allows you to define anonymous functions, which are functions without a name. These are often used as callback functions, which are functions that are passed as arguments to another function and called at a later time.
let add = function(num1, num2) {
return num1 + num2;
}
let result = add(2, 3);
console.log(result); // Outputs 5
In this example, we define an anonymous function called "add", which takes two parameters: "num1" and "num2". We then call this function and store the result in the "result" variable, which is output to the console.
In conclusion, JavaScript functions are an important part of any JavaScript program. They allow you to group code together, give it a name, and reuse it throughout your code. By understanding the basics of functions, you will be able to write more efficient and organized code, which will ultimately lead to better programs.