How do I call for a certain variable or another depending on a string I have

Question

I have two variables, varL and varR, which have the information that they are L and R respectively. Depending on wether a third object has as imput 'L' or 'R', I would like to reference varL or varR respectively. Is there any way to do this?

Specifically, varL and varR are arrays. If the third object has as imput 'L', I would like to have access to varL[i] for some i, and the same goes for 'R'. I know this is not even remotely correct, but I was looking for something like

(var +'L')[i] or something

For just two variables, use a simple condition that evaluates to either. For more complex scenarios, use an appropriate data structure that allows lookup by key instead of multiple variables. — Bergi, Apr 06 '17 at 05:33
Why is it not advisable to use eval? It worked just fine, thanks! — popeye, Apr 06 '17 at 05:50
@GastonMaffei [Why is it not advisable to use eval?](https://www.google.co.jp/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=why+is+it+not+advisable+to+use+eval&*) — JLRishe, Apr 06 '17 at 05:58
@GastonMaffei http://stackoverflow.com/questions/86513/why-is-using-the-javascript-eval-function-a-bad-idea — Bergi, Apr 06 '17 at 06:07

score 1 · Accepted Answer · answered Apr 06 '17 at 05:22

1

var varL;
var varR;

function getInput(input) {
  return (input == 'L') ? varL : varR;
}

?

answered Apr 06 '17 at 05:22

mwkrimson

115
1
9

score 0 · Answer 2 · answered Apr 06 '17 at 05:25

If you have input value then you can check and use corresponding array like below in your loop

var testL=[4,5,6];
var testR=[4,5,6];


var input='L';

if(input=='L'){
  console.log(testL[0]);    //replace 0 with i index
}else if(input=='R'){
 console.log(testR[0]);      //replace 0 with i index
}

score 0 · Answer 3 · answered Apr 06 '17 at 05:56

Your question is the XY problem. Instead of asking "How can I access a variable by a dynamic name?", you should be asking "How can I access the needed value for L or R dynamically?"

One simple way to make it work is to store the values in an object with .L and .R properties. Then it's very simple to access the needed value:

var myVar = {
  L: [1, 2, 3],
  R: [3, 4, 5]
};

var direction = 'L';

console.log(myVar[direction]);

direction = 'R';

console.log(myVar[direction]);

score -2 · Answer 4 · answered Apr 06 '17 at 05:22

-2

Try to access it from window object

window[("var"+"L")]

It will work !!

or eval

eval(("var"+"L"))[i]

answered Apr 06 '17 at 05:22

RITESH ARORA

487
3
11

ok, so if I have 'L' as input of my third object, and so I want to access the ith element of varL, I just type window["var"+"L"][i]? – popeye Apr 06 '17 at 05:25
are you doing this on node ?just curious why window not worked – RITESH ARORA Apr 06 '17 at 05:51
1

@RITESHARORA `window[...]` would only work if `varL` and `varR` are global variables. – JLRishe Apr 06 '17 at 05:59
Yes i was also thinking same but do not know if variables are globals or not thats why also mentioned eval – RITESH ARORA Apr 06 '17 at 06:08

How do I call for a certain variable or another depending on a string I have

4 Answers4