if value is in array js code example

Example 1: how to check if item is in list js

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

Example 2: 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");
}

Example 3: check if an element is already in an array

private boolean ZitAlInArray(int value, List<Integer> list) {
  return array.indexOf(value) > -1;
}

private boolean zitAlInArray(int[] array, int index) {
		for (int i = 0; i < index; i++) {
			if (array[i] == array[index]) {
				return true;
			}
		} 
		return false;
	}