Javascript - Verify the presence of two elements within an array

Question

Javascript - Verify the presence of two elements within an array

How can I ensure that both ages 10 and 18 exist in a JavaScript array of ages, rather than just one?

var ages = [3, 10, 18, 20];
ages.filter(age => age === 10 || age === 18); // returns 10 and 18
ages.filter(age => age === 10 && age === 18); // returns null

Using && doesn't guarantee the existence of both ages as it results in null. Is there a more elegant way to achieve this using a single statement, rather than combining separate find/filter checks?

In essence, if I check for the presence of 10 (exists) and 21 (does not exist) within the ages array, it should return null or false, indicating that one of them is missing.

javascript arrays

Answer 1

Answer №1

To check if a value is included in an array, you can use the includes function:

var ages = [3, 10, 18, 20];
console.log(ages.includes(10) && ages.includes(18));

Another approach is to utilize the indexOf method:

arr.indexOf(searchElement)

arr.indexOf(searchElement, fromIndex)

var ages = [3, 10, 18, 20];
console.log(ages.indexOf(10)!=-1 && ages.indexOf(18)!=-1);

The findIndex method is also available for this purpose. It works similarly to indexOf, but with some distinctions:

Array.prototype.indexOf() requires a value as input, suitable for arrays of primitive types like Number, String, or Boolean.

Array.prototype.findIndex() takes a callback function as its first parameter, particularly beneficial when dealing with arrays of objects.

var ages = [3, 10, 18, 20];
var bool=ages.findIndex(a=>a==10)!=-1 && ages.findIndex(a=>a==18)!=-1;
console.log(bool);

Answer 2

To check if a value is included in an array, you can use the includes function:

var ages = [3, 10, 18, 20];
console.log(ages.includes(10) && ages.includes(18));

Another approach is to utilize the indexOf method:

arr.indexOf(searchElement)

arr.indexOf(searchElement, fromIndex)

var ages = [3, 10, 18, 20];
console.log(ages.indexOf(10)!=-1 && ages.indexOf(18)!=-1);

The findIndex method is also available for this purpose. It works similarly to indexOf, but with some distinctions:

Array.prototype.indexOf() requires a value as input, suitable for arrays of primitive types like Number, String, or Boolean.

Array.prototype.findIndex() takes a callback function as its first parameter, particularly beneficial when dealing with arrays of objects.

var ages = [3, 10, 18, 20];
var bool=ages.findIndex(a=>a==10)!=-1 && ages.findIndex(a=>a==18)!=-1;
console.log(bool);

Javascript - Verify the presence of two elements within an array

Answer №1

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