The eval() method in Java Script evaluates  or  executes its argument. If  the argument is an expression, it evaluates the expression. If  it’s one or more JavaScript statements, eval() executes the statements. This function was used to evaluate a string as JavaScript code, but it is now considered deprecated because it can introduce security vulnerabilities and  is often unnecessary

eval() Function Parameters:

This function accepts a single parameter as mentioned below:

String: A string representing a JavaScript expression, statement, or sequence of statements. The  expression can include variables and properties of existing objects

Return Value of eval() Function

The completion value of evaluating the given code is returned by using eval(). If the completion value is empty, undefined is returned 

Direct eval: It’s called  by the eval identifier directly

Indirect eval: It’s invoked via another property, such as window. eval() or when using set Timeout,  set Interval,  or the function constructor

DO NOT USE eval():

Security Risk: Evaluated code posses security vulnerabilities

Performance Impact: Slows down execution due to runtime parsing

Readability: Decreases code readability and maintainability

Strict Mode Compatibility: Not allowed in strict mode

Alternatives: Safer alternatives are available  for dynamic code execution

Exceptions of eval() in JavaScript:

If we pass a non- string argument to eval in JavaScript, it returns the same argument without any change

let arr = [1, 2, 3];
let output = eval(arr);
console.log(output);

Output:
[1, 2, 3]

In the above example, we passed an array into the eval() function because it is  non-string argument, the function returned the same array without any changes to it