How to check several local variables for the same if conditions

Question

Alright, I find the code below to be quite repetitive and annoying. Any other way to refactor the code without using an array as a starting point (that is, to avoid using array[x], array[y], array[z] later on in the code as a result of starting with an array because x,y,z are completely unrelated and it makes no sense to group them for the sake of readability)

var x = "";
var y = "";
var z = "";
...

...variables get set

if(x != undefined && x != "")
    doSomethingHere();

if(y != undefined && y != "")
    doSomethingThere();

if(z != undefined && z != "")
    doSomethingElse();
...

Answer 1

Is there a reason you initialize x,y and z to "" ?

If you just do

 var x;

 ..... maybe set x .....

 if (x)
    doSomething()

You save quite a lot of fuzz. You can do the same for y and z ;) The initial value of x is undefined, which you can check with if (x), which means the same as if (x != undefined)

Answer 2

I'm guessing the original should have used y != undefined and doSomething () is the same function in all cases:

if((x != undefined && x != "") || 
   (y != undefined && y != "") ||
   (z != undefined && z != ""))
    doSomething();

Answer 3

First of all, because both undefined and the empty string ("") evaluate as "false" in javascript, you can change your conditionals to:

if (x) 
     doSomething();
if (y) 
     doSomething();
if (z) 
     doSomething();

If the Something to be Done is always the same, you can certainly do

if (x || Y || z)
     doSomething();

Answer 4

At very least you can factor out your validation rules to their own function:

function IsValid(x)
{
    return (x != undefined && x != "");
}

var x = "";
var y = "";
var z = "";
//...

//...variables get set

if(IsValid(x)) doSomething();
if(IsValid(y)) doSomething();
if(IsValid(z)) doSomething();

Answer 5

So to follow up on krosenvold's answer I think what you want is

var x;
var y;
var z;

// do stuff

if (x||y||z)
  doSomething();

Which is much neater

Answer 6

If you're trying to avoid repetition, be it vertical (var x;\r\n;var y;\r\n...) or horizontal (if (x || y || z || ...), a nice way to tidy things up is to gather your variables into an object as properties:

var vars = {
    x: 42,
    y: "",
    z: undefined
};

for (var v in vars) {
    var value = vars[v];

    if (value != undefined && value != "") {
        doSomething();
    }
}

On top of that, if the action to be taken is different for each variable, you can also define an "actions" structure:

var actions = {
    x: doSomething,
    y: doSomethingElse,
    z: doSomething
};

for (var v in vars) {
    var value = vars[v];

    if (value != undefined && value != "") {
        actions[v]();
    }
}

Answer 7

In addition to what joel said you could also do the following:

function doOnValid(x, func){
 if(x != undefined && x != "") func();
}

Then you could do:

doOnValid(x, doSomething);
doOnValid(y, doSomethingElse);
doOnvalid(z, function() { /*Yay lambda function*/ });

Answer 8

This is about as concise as I can make it, assuming you want a unique action for each condition.

(x && doX());
(y && doY());
(z && doZ());

This works because your particular variable test just reduces to the value of the variable. You can, of course, also write a custom condition function:

function is_valid(x){
    // return true or false
}

( is_valid(x) && doX() );
( is_valid(y) && doY() );
( is_valid(z) && doZ() );