# NaN The global NaN property is a value representing Not-A-Number. To tell if a value is NaN, use isNaN() to most clearly determine whether a value is NaN. ## Issue in Minecraft **Testing against NaN** In vanilla JavaScript, you are able to validate if a value equals NaN by doing `40 === NaN`. This is not the case for Minecraft script engine, where NaN equals any integer. For example, ```js NaN === 4 // returns `true` instead of false. ``` A workaround is to use `isNaN()` or `Number.isNaN()`, since these functions are not broken. ```js isNaN(40); // false Number.isNaN(-60); // false ``` ## Learn More https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/NaN