Jul 8, 2025 · The logical OR (||) (logical disjunction) operator for a set of operands is true if and only if one or more of its operands is true. It is typically used with boolean (logical) values. When it is, it returns a Boolean value.

A JavaScript function is defined with the function keyword, followed by a name, followed by parentheses (). Function names can contain letters, digits, underscores, and dollar signs (same rules as variables).

Jul 8, 2025 · To use a function, you must define it somewhere in the scope from which you wish to call it. See also the exhaustive reference chapter about JavaScript functions to get to know the details. A function definition (also called a function declaration, or function statement) consists of the function keyword, followed by: The name of the function.

Inspired by underscore, the final isFunction function is as follows: return functionToCheck && {}.toString.call(functionToCheck) === '[object Function]'; Note: This solution doesn't work for async functions, generators or proxied functions. Please see …

Summary: in this tutorial, you will learn about JavaScript functions and how to use them to structure the code into smaller and more reusable units. When developing an application, you often need to perform the same action in many places. For example, you may want to show a message whenever an error occurs.

Oct 14, 2022 · We’ve already seen examples of built-in functions, like alert(message), prompt(message, default) and confirm(question). But we can create functions of our own as well. To create a function we can use a function declaration. It looks like this: function showMessage() { alert( 'Hello everyone!' ); }

Jun 28, 2025 · Functions in JavaScript are reusable blocks of code designed to perform specific tasks. They allow you to organize, reuse, and modularize code. It can take inputs, perform actions, and return outputs. A function definition is sometimes also termed a function declaration or function statement.

We can create a function in JavaScript using the function keyword: console.log("Hello World!"); Here, we have created a simple function named greet() that prints Hello World! on the screen. Our function contains the following parts: Function Keyword - The …

Learn what are functions in JavaScript. Explore the basics of functions in JavaScript, including anonymous and arrow functions, and learn how to organize your code using functions.

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