https://stackoverflow.com › questions › 52389757

If nothing is found, it returns undefined. Your code should work, but yes, one way to do it in one line (if you want) is to use: getExecsFromTour(tourId){ return (this.repInfo.find(el => el.id == tourId) || {}).execs || []; }

https://stackoverflow.com › questions › 3390396

If you are interested in knowing whether the variable hasn't been declared or has the value undefined, then use the typeof operator, which is guaranteed to return a string: if (typeof myVar !== 'undefined') Direct comparisons against undefined are troublesome as undefined can be overwritten. window.undefined = "foo";

https://developer.mozilla.org › fr › docs › Web › JavaScript › Reference › Global_Objects › Array › find

La méthode find() renvoie la valeur du premier élément trouvé dans le tableau qui respecte la condition donnée par la fonction de test passée en argument. Sinon, la valeur undefined est renvoyée.

https://developer.mozilla.org › ... › docs › Web › JavaScript › Reference › Global_Objects › Array › find

The find() method of Array instances returns the first element in the provided array that satisfies the provided testing function. If no values satisfy the testing function, undefined is returned. If you need the index of the found element in the array, use findIndex().

https://byby.dev › js-check-undefined

Using typeof operator to check if a property is undefined. It will return "undefined" for both undefined and undeclared values, so it cannot tell if a property exists or not. It will return "object" for both null and object values, so it cannot distinguish between them. let obj = {a: 1}; . console.log(typeof obj); // "object" .

https://masteringjs.io › tutorials › fundamentals › check-if-property-is-undefined

You can combine these two sections to check if an object has a property and that property is undefined: function hasUndefinedKey(obj, key) {. return key in obj && obj[key] === undefined; } or. function hasUndefinedKey(obj, key) {. return obj.hasOwnProperty(key) && obj[key] === undefined; }

https://developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › ...

The hasOwnProperty() method returns true if the specified property is a direct property of the object — even if the value is null or undefined. The method returns false if the property is inherited, or has not been declared at all.

https://www.freecodecamp.org › news › javascript-check-if-undefined-how-to-test-for...

console.log(myArr[7]); // undefined. In this article, you will learn the various methods and approaches you can use to know if a variable is undefined in JavaScript. This is necessary if you want to avoid your code throwing errors when performing an operation with an undefined variable.