JavaScript In Operator

• Description
• Syntax
• Footnotes

Description

~in~[fn:in] tells us if indices inside an [JavaScript Arrays](JavaScript Arrays) or [JavaScript Objects](JavaScript Objects) have no associated element.

Syntax

const arr = ['a',,'b']
console.log(0 in arr) // true
console.log(1 in arr) // false
console.log(2 in arr) // true
console.log(arr[1]) // undefined

const car = { make: “Honda”, model: “Accord”, year: 1998 };

console.log(“make” in car); // true

delete car.make;
if (“make” in car === false) {
car.make = “Suzuki”;
}

console.log(car.make); //Suzuki

Footnotes

[fn:in]https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/in