Can anyone explain this code

Question

x=[5,10,15];
x.join = x.shift;

if(x == 5 && x == 10 && x==15)
console.log("good");

//why the above condition return true?

Answer 1

x = [5,10,15]; /* so */

x = 5,
x = 10,
x = 15,

so x.join = 5, 10, 15 ( x.shift)

if x == 5 10 && 15 /* always true */
therefore console.log("good");