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 

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?

12 Answers

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

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

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

You could try this:

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

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

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.

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; } 

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.

I prefer the style

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

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:

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')); 

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.