JS Daily 36 - Eval

What is the output of following code?

var b = 20;
eval('var b = 10');
console.log(b);

The output is 10.

eval() evaluates the passed argument string as an expression. Here, the expression is changing the value of b from 20 to 10. That is why the output prints 10.

Since eval() can dynamically change the scope and flow of code, it is advised NOT to use it whenever possible.