Need to get the value of a variable which is sent as a string?

Question

Hi

I'm sending a string as parameter to a function, but i already have a global variable in that name, i want to get the value of that variable but its sending as undefined..

My example code

i have a array as reg[0][0],reg[0][1],reg[1][0],reg[1][0],reg[2][0],reg[2][1]

and i have some global variables as tick1, tick2, tick3...

it will either have the values as 0,1 or 2

and in a function i called

calc_score(id) //id will return as either tick1,tick2,tick3
{
    alert(eval("reg[id][1]")); // it should return the value of reg[0][1] if id is 0

}

But its not working.

The id wont be a numeral it will be string .. So how can i do this?

Answer 1

Oh! You change the code like the following:

calc_score(id) //id will return as either tick1,tick2,tick3
{
    alert(eval("reg[" + id + "][1]")); // it should return the value of reg[0][1] if id is 0

}

Answer 2

Use this:

alert(reg[Number(id)][1]);

of course you should check that id can be cast to a number before you do it. I don't really think you need the eval, unless you are trying to do something else that you haven't mentioned.

Answer 3

You shouldn't use eval for things like this. If you need to convert id to a number, use the unary + operator:

calc_score(id) //id will return as either tick1,tick2,tick3 
{ 
    alert(reg[+id][1]); // it should return the value of reg[0][1] if id is 0 
} 

or parseInt()

calc_score(id) //id will return as either tick1,tick2,tick3 
{ 
    alert(reg[parseInt(id, 10)][1]); // it should return the value of reg[0][1] if id is 0 
} 

---

If you need to parse a string like "tick1, tick2" then you have a few options. If the first part will always be "tick", you can slice the end off the string like so:

calc_score(id)
{
    id = +id.slice(4);         // or +id.substring(4) if you prefer
    alert(reg[id][1]); 
}

If tick1, tick2, tick3 are global variables, then instead of using eval(), you should reference them via the window object like so:

calc_score(id)   //id will return as either "tick1","tick2","tick3"
{
    alert(window[id]);
}