javascript primitive string

Let's see below example

let s1 = '2 + 2'              // creates a string primitive
let s2 = new String('2 + 2')  // creates a String object
console.log(eval(s1))         // returns the number 4
console.log(eval(s2))         // returns the string "2 + 2"

String primitives and String objects

String primitives and String objects also give different results when using eval(). Primitives passed to eval are treated as source code; String objects are treated as all other objects are

ref