Javascript command to check values in set?

Question

Im trying to find a creative way/patch in order to minimize this line :

 if(myParam == '1' || myParam == 'a' || myParam == '*' || myParam == '@' || myParam == undefined || myParam == null || myParam == ' ')
    {...
    }

One solution is the use indexOf - but it is not cross browser (I could write my own func to behave like indexOf - but I dont want to ).

So I tried the in operator

But the in operator deals only with object properties names and indexes

So I tried this (object properties):

   if(window.lala in {
    '*': 0,
    'a': 0,
    '@': 0,
    ' ': 0,
    undefined: 0,
    null: 0
}) alert('1')

and I think it is working.

2 question please :

question #1

is it safe for property name to be [undefined] or [' '] or [null] ? will it always work ?

question #2 Is there any other solution for doing this ?

(Case/switch can be done too, I know... )

jfriend00 · Accepted Answer · 2012-10-11 07:56:06Z

1

What you have won't work for undefined. You can have a property named "undefined", but that's a string name, not the actual undefined value. You may get a match via type conversion, but it will also match if you have a string named "undefined" too which is not something you want.

I would suggest a more explicit test that uses === to avoid any type conversions. There are several ways to do it that are slightly less verbose than what you had:

if (myParam === null || myParam === undefined || 
    (myParam && myParam.length == 1 && "1a*@ ".indexOf(myParam) !== -1) {
   // code here
}

Or you can make an array and your own cross browser function (or use a polyfill for Array.indexOf() to search an array which can hold all the values:

function inArray(val, array) {
    for (var i = 0; i < array.length; i++) {
        if (array[i] === val) {
            return(true);
        }
    }
    return(false);
}

var testValues = [null, undefined, "1", "a", "*", "@", " "];
if (inArray(window.lala, array)) {
    // your code here
}

You can use the object form you were experimenting with and just use explicit tests for null and undefined, but I think the string.indexOf() suggestion in my first proposal is simpler. Anyway, here's a safe form using the object

if (myParam === null || myParam === undefined || 
    (myParam && (myParam in {"*":0, "1":0, "a":0, "@":0, " ":0})) {
   // code here
}

My recommendation would be the first option as I think it's the cleanest and it's also really easy to extend by just adding more chars to the test string.

edited Oct 11, 2012 at 7:56

answered Oct 11, 2012 at 7:37

jfriend00

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7 Comments

jfriend00 Over a year ago

@RoyiNamir - but the property name in your test object is not undefined. All property names are strings so undefined !== "undefined" so it won't match in your object lookup.

Royi Namir Over a year ago

I dont get it.

if(undefined in {     '0': 0,     '*': 0,     'a': 0,     '@': 0,     ' ': 0,     undefined: 0,     null: 0 }) alert('1') //

it does alert

Felix Kling Over a year ago

@jfriend00: When you use in, the value you test for will be converted to a string. That's why it "works".

jfriend00 Over a year ago

@RoyiNamir - you are living dangerously via a type conversion. Note that if("undefined" in { '0': 0, '*': 0, 'a': 0, '@': 0, ' ': 0, undefined: 0, null: 0 }) alert('1') runs the alert too.

Royi Namir Over a year ago

@FelixKling I think you wanted to tell me that :-)

|

Felix Kling · Accepted Answer · 2012-10-11 07:39:36Z

1

Is it safe for property name to be [undefined] or [' '] or [null] ? will it always work?

All property names are converted to strings, which means you cannot distinguish between the number 0 and the string '0' and not between the value null (undefined) and the string 'null' ('undefined').

Treating numbers as numeric strings is probably fine in your case, for undefined and null, I would just add an extra test:

if(value == null || value in exclude) {
    // ...
}

value == null is true if value is null or undefined.

answered Oct 11, 2012 at 7:39

Felix Kling

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Comments

happyCoda · Accepted Answer · 2012-10-11 07:49:30Z

0

1: it's better to use 'undefined' and 'null' as names of your object, because when you walk through it with for in loop it checks for string representations of a property(you can check it if you do a:

 for(prop in obj) typeof(prop) //this will be a string

2: You can also store your values in array and do recursion:

 var vals = ['*', 'a', '@', ' ', undefined, null], param = '@', i = 0;

function checkVals(param, vals, i) {
    if (vals[i] && param === vals[i]) {
        console.log(1);
        return;
    } 

    checkVals(param, vals, i + 1);
}

checkVals(param, vals, i);

answered Oct 11, 2012 at 7:49

happyCoda

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2 Comments

Felix Kling Over a year ago

Why would you use recursion instead of a simple loop?

happyCoda Over a year ago

You can use simple loop if you want. I just show one way how this problem can be solved :)

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