funktionsuttryck

A Funktionsuttryck, often translated as function expression in English, is a way to define a function in JavaScript. Unlike a function declaration, a function expression defines a function as part of an expression. This means the function can be assigned to a variable, passed as an argument to another function, or returned from a function.

When a function expression is created, the function itself is an anonymous entity. It can optionally be given a name, which can be useful for recursion or debugging, but this name is not accessible outside the function's scope. The function is created when the expression is evaluated.

One key difference between function declarations and function expressions is hoisting. Function declarations are hoisted to the top of their scope, meaning they can be called before they are defined in the code. Function expressions, however, are not hoisted in the same way. The variable that holds the function expression is hoisted, but the function itself is not assigned to the variable until the line of code where the expression is defined is executed. Therefore, attempting to call a function expression before its definition will result in a TypeError.

Function expressions are commonly used for creating immediately invoked function expressions (IIFEs), which are executed as soon as they are defined, and for creating callback functions. They offer flexibility in how functions are used and manipulated within JavaScript code.