Eval function in javascript

Question

any ideas about eval function in js ?
because it seems very usefull but some says that it can be harmfull
can someone explain this.

Answer 1

Hello, Youness Oubelkacem !
In the simplest case, eval just executes the code, for example:

var a = 1;
(function() {
var a = 2

eval('alert(a)');
// 2
}) ()

But he can not only execute the code, but also return the result.

The eval call returns the last calculated expression, for example:

alert(eval('1 + 1')); // 2

Answer 2

i've seen it being used in calculators i think but other that i have no clue

Answer 3

It evaluates codes or math expressions I think

Answer 4

I used eval in js to bring out the equality value in my simple calculators

Answer 5

yes it's very usefull in a calculator ...
thanks anyway

Answer 6

thanks Alexander Sokolov for your clarification .
but still wondring why this function is harmfull

Answer 7

its dangerous because people can use it to hack