if value in list javascript 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: array includes

let storyWords = ['extremely', 'literally', 'actually', 'hi', 'bye', 'okay']
let unnecessaryWords = ['extremely', 'literally', 'actually' ];

let betterWords = storyWords.filter(function(word) {
  return !unnecessaryWords.includes(word);
});
console.log(betterWords) // ['hi' 'bye' 'okay]

Example 3: 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");
}