JAVASCRIPT

how to check if an element is in an array javascript

const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.includes("Mango");

how to check if item is in list js

var myList=["a", "b", "c"];
mylist.includes("d")//returns true or false

How do I check if an array includes a value in JavaScript?

Modern browsers have Array#includes, which does exactly that and is widely supported by everyone except IE:

console.log(['joe', 'jane', 'mary'].includes('jane')); //true

javascript check if array has a certain element

// check if an array INCLUDES a certain value

//array for includes()
let numbers = [1, 2, 3, 4, 5]

// either true or false 
numbers.includes(2) // returns true, the numbers array contains the number 2

numbers.includes(6) // returns false, the numbers array DOESNT contain the number 6

javascript check if in array

var extensions = ["image/jpeg","image/png","image/gif"];          
if(extensions.indexOf("myfiletype") === -1){
	alert("Image must be .png, .jpg or .gif");
} 

how to check if array contains an item javascript

let isInArray = arr.includes(valueToFind[, fromIndex])
// arr         - array we're inspecting
// valueToFind - value we're looking for
// fromIndex   - index from which the seach will start (defaults to 0 if left out)
// isInArray   - boolean value which tells us if arr contains valueToFind

How to Check if an Item is in an Array in JavaScript Using Array.includes()

const nums = [ 1, 3, 5, 7];
console.log(nums.includes(3));
// true

javascript check if array is in array

var array = [1, 3],
    prizes = [[1, 3], [1, 4]],
    includes = prizes.some(a => array.every((v, i) => v === a[i]));

console.log(includes);

how to check if an element is in array javascript

array.includes('element that need to be checked') //returns true or false 

check items in array javascript

function checkAllEven(arr) {
  return arr.every(function(x){
	 return	x % 2 === 0
	})
}

//using "every" to check every item in array.

javascript - Determine whether an array contains a value

var contains = function(needle) {
    // Per spec, the way to identify NaN is that it is not equal to itself
    var findNaN = needle !== needle;
    var indexOf;

    if(!findNaN && typeof Array.prototype.indexOf === 'function') {
        indexOf = Array.prototype.indexOf;
    } else {
        indexOf = function(needle) {
            var i = -1, index = -1;

            for(i = 0; i < this.length; i++) {
                var item = this[i];

                if((findNaN && item !== item) || item === needle) {
                    index = i;
                    break;
                }
            }

            return index;
        };
    }

    return indexOf.call(this, needle) > -1;
};