js if element matches in array code example

Example 1: loop array and check if value matches in js

var arr1 = [1, 3, 4,];

var arr2 = [
  {
    id: 1,
    title: 'Title 1',
   },
  {
    id: 2,
    title: 'Title 2',
   },
];

var res = arr2.filter(i => arr1.includes(i.id));

console.log(res);

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");
}