What will be the output of the following code and why:

(function(){
    var a=b=5
})();
console.log(b);
console.log(a);

This code defines an anonymous self-executing function that declares a variable a and assigns it the value of b, which is in turn assigned the value of 5.

When you run the code, the following output will be produced in the console:

console.log(b) // 5
console.log(a) // Uncaught ReferenceError: a is not defined

The first console.log statement outputs the value of b, which was declared in the global scope (outside of any function) and is therefore accessible from anywhere in your code.

The second console.log statement, however, throws an error because a was declared inside the anonymous self-executing function and is not accessible from the global scope. This demonstrates the difference between variable declarations with the var keyword, which have function scope, and variables declared without var, let, or const, which have global scope.