I am aware of it being frowned upon to do something like write C# in JavaScript. (see this if you don't know what I'm talking about)
But as a judgement call, I think we could stand to have a relatively simple check for values that are null or empty, so I'm looking for feedback on this implementation of String.isNullOrEmpty.
String.isNullOrEmpty = function (value) {
return (!value || value == undefined || value == "" || value.length == 0);
}
Starting with:
return (!value || value == undefined || value == "" || value.length == 0);
Looking at the last condition, if value == "", it's length MUST be 0. Therefore drop it:
return (!value || value == undefined || value == "");
But wait! In JS, an empty string is false. Therefore, drop value == "":
return (!value || value == undefined);
And !undefined is true, so that check isn't needed. So we have:
return (!value);
And we don't need parentheses:
return !value
Q.E.D.
There are just a few revisions I would make.
First, always use === instead of == in Javascript. You can read more about that on Stack Overflow.
Second, since undefined is mutable, I would reccomend using
typeof value === "undefined"
instead of
value === undefined
Third, I would remove the !value and value === "" conditions. They are redundant.
I would use a slightly different approach than you:
String.isNullOrEmpty = function(value) {
return !(typeof value === "string" && value.length > 0);
}
This checks if the type of the value is "string" (and thus non-null and not undefined), and if it is not empty. If so, it is not null or empty.
Note that this returns true for non-string inputs, which might not be what you want if you wanted to throw an error for an unexpected input type.
Your function unexpectedly returns true for the following non-string values:
false0Number.NaN[[]][]It's quite possible that !value though it is similarly sloppy, would suffice, in which case you wouldn't need to define this function at all. But if you create a function that is named isNullOrEmpty, then it should do just that.
function String.isNullOrEmpty(value) {
return value == null || value === "";
}
Note that value == null is shorthand for value === null || value === undefined.
You should use Object.prototype.isNullOrEmpty = function() { alert(this) }. This ties it to the String object in all instances. This would start to give you access to use strings and variables like "".isNullOrEmpty or var x = null; x.isNullOrEmpty();
If your intent is to use it as a function to pass in variables: String.isNullOrEmpty();
null won't work.
\$\endgroup\$
undefined either.
\$\endgroup\$
Ryan and seand are spot on: This achieves your end.
Object.prototype.isNullOrEmpty = function(value){
return (!value);
}
This is what I love about JavaScript!
toStringonvalue? \$\endgroup\$return !value;suffice? \$\endgroup\$