[javascript] Javascript isnull

This is a really great function written in jQuery to determine the value of a url field:

$.urlParam = function(name){
    var results = new RegExp('[\\?&]' + name + '=([^&#]*)').exec(window.location.href);
    return results[1] || 0;
}

// example.com?someparam=name&otherparam=8&id=6
$.urlParam('someparam'); // name
$.urlParam('id'); // 6
$.urlParam('notavar'); // null

http://snipplr.com/view/11583/retrieve-url-params-with-jquery/

I would like to add a condition to test for null, but this looks kind of klunky:

if (results == null) {
    return 0;
} else {
    return results[1] || 0;
}

Q: What's the elegant way to accomplish the above if/then statement?

You can also use the not operator. It will check if a variable is null, or, in the case of a string, is empty. It makes your code more compact and easier to read.

For example:

var pass = "";
if(!pass)
    return false;
else
    return true;

This would return false because the string is empty. It would also return false if the variable pass was null.

I prefer the style

(results || [, 0]) [1]

if (typeof(results)!='undefined'){ 
    return results[1];
} else { 
    return 0; 
};

But you might want to check if results is an array. Arrays are of type Object so you will need this function

function typeOf(value) {
    var s = typeof value;
    if (s === 'object') {
        if (value) {
            if (value instanceof Array) {
                s = 'array';
            }
        } else {
            s = 'null';
        }
    }
    return s;
}

So your code becomes

if (typeOf(results)==='array'){
      return results[1];
}
else
{
      return 0;
}

Why not try .test() ? ... Try its and best boolean (true or false):

$.urlParam = function(name){
    var results = new RegExp('[\\?&]' + name + '=([^&#]*)');
    return results.test(window.location.href);
}

Tutorial: http://www.w3schools.com/jsref/jsref_regexp_test.asp

return (results||0) && results[1] || 0;

The && operator acts as guard and returns the 0 if results if falsy and return the rightmost part if truthy.

You could try this:

if(typeof(results) == "undefined") { 
    return 0;
} else {
    return results[1] || 0;
}

return results==null ? 0 : ( results[1] || 0 );

return results == null ? 0 : ( results[1] || 0 );

I'm using this function

function isNull() {
    for (var i = 0; i < arguments.length; i++) {
        if (
            typeof arguments[i] !== 'undefined'
            && arguments[i] !== undefined
            && arguments[i] != null
            && arguments[i] != NaN
            && arguments[i] 
        ) return arguments[i];
      }
}

test

console.log(isNull(null, null, undefined, 'Target'));

the most terse solution would be to change return results[1] || 0; to return (results && results[1]) || 0.

All mentioned solutions are legit but if we're talking about elegance then I'll pitch in with the following example:

//function that checks if an object is null
var isNull = function(obj) {
  return obj == null;
}            

if(isNull(results)){
 return 0;
} else {
  return results[1] || 0;
}

Using the isNull function helps the code be more readable.