Undefined -- from Wolfram MathWorld
Dec 22, 2025 · An expression in mathematics which does not have meaning and so which is not assigned an interpretation. For example, division by zero is undefined in the field of real numbers.
Undefined Expressions & Numbers in Math | Functions & Examples
Discover what an undefined expression in math is. Understand what an undefined number for a function is. Learn when a function is undefined with...
How to handle 'undefined' in JavaScript - Stack Overflow
Dec 31, 2009 · typeof foo !== 'undefined' window.foo !== undefined 'foo' in window The first two should be equivalent (as long as foo isn't shadowed by a local variable), whereas the last one …
UNDEFINED Synonyms: 50 Similar and Opposite Words | Merriam …
Synonyms for UNDEFINED: vague, faint, hazy, undetermined, unclear, indistinct, nebulous, indefinite; Antonyms of UNDEFINED: clear, definite, distinct, obvious ...
What does "undefined" mean? | Math Forums
Jun 27, 2023 · What is the exact definition of "undefined"? My textbook explains it as "a fraction with a denominator of 0" but the term seems to be broader than that.
How to Detect an Undefined Object Property in JavaScript
Jul 23, 2025 · Your All-in-One Learning Portal: GeeksforGeeks is a comprehensive educational platform that empowers learners across domains-spanning computer science and …
How to Check for Undefined in JavaScript
Mar 4, 2020 · What if a JavaScript value is undefined? In JavaScript programming, you will encounter the primitive data type undefined, which indicates the absence of a value. Variables …
The difference between `typeof x !== "undefined"` and `x != null`
This works because when someone writes undefined = "foo" he only lets the name undefined reference to a new value, but he doesn't change the actual value of undefined.
Handling Undefined Variable Errors in JavaScript
Mar 26, 2023 · <p>Handling undefined variable errors is a common challenge that developers face when working with JavaScript. These errors can be confusing, especially for those who …
Undefined - Binding of Isaac: Rebirth Wiki
Undefined is an unlockable activated item. Teleports Isaac to the Treasure Room, the Secret Room, the Super Secret Room or I AM ERROR. There is also a 1% chance of teleporting into …
undefined - JavaScript | MDN
6 days ago · The undefined global property represents the primitive value undefined. It is one of JavaScript's primitive types.
null et undefined | web.dev
Découvrez comment utiliser les types de données "null" et "undefined" de JavaScript.
nulo e indefinido | web.dev
Aprende a usar los tipos de datos `null` e `undefined` de JavaScript.
JavaScript Null vs Undefined: Key Differences & When to Use Each
Nov 8, 2024 · In JavaScript, managing the absence of value is fundamental, and two key terms—null and undefined—serve this purpose. These two concepts