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).

JavaScript functions are defined with the function keyword. You can use a function declaration or a function expression. Earlier in this tutorial, you learned that functions are declared with the following syntax: Declared functions are not executed immediately.

Mar 22, 2025 · A function in JavaScript is similar to a procedure—a set of statements that performs a task or calculates a value, but for a procedure to qualify as a function, it should take some input and return an output where there is some obvious relationship between the …

JavaScript variables have 3 types of scope: Before ES6 (2015), JavaScript variables had only Global Scope and Function Scope. ES6 introduced two important new JavaScript keywords: let and const. These two keywords provide Block Scope in JavaScript. Variables declared inside a { } block cannot be accessed from outside the block:

Jan 18, 2019 · I am trying to understand storing a function as a variable. If I have the following function: return 2 * 2 . I know that the variable test has the value of 4, which makes sense. However, in this example: function foo() { console.log("HEY") foo() //logs "HEY" in the console. var test = foo() . test // does NOT log "HEY" in the console.

6 days ago · 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.

Jan 29, 2025 · Variables in JavaScript can be declared using var, let, or const. JavaScript is dynamically typed, so variable types are determined at runtime without explicit type definitions. 1. JavaScript var keyword.

Jul 15, 2024 · In JavaScript, every function is actually a Function object. Creates a new Function object. Calling the constructor directly can create functions dynamically but suffers from security and similar (but far less significant) performance issues to eval().

Feb 10, 2025 · When a variable is declared using var, it is function-scoped or globally-scoped, depending on where it is declared. Syntax. It declares a variable using var, assigns it a value, and allows it to be re-declared or updated within its scope. 1. Function Scope. Variables declared using var are function-scoped.

Here's a quick example of function and function expression. You can read the rest of the tutorial for more. console.log("Hello World!"); // store a function in the displayPI variable // this is a function expression let displayPI = function() { console.log("PI = 3.14"); // call the greet() function . // call the reply() function .