Answer by Avinash Maurya for typeof !== "undefined" vs. != null
var bar = null;console.log(typeof bar === "object"); //true yes //because null a datatype of objectvar barf = "dff";console.log(typeof...
View ArticleAnswer by Avinash Maurya for typeof !== "undefined" vs. != null
function greet(name, greeting) { name = (typeof name !== 'undefined') ? name : 'Student'; greeting = (typeof greeting !== 'undefined') ? greeting : 'Welcome'; console.log(greeting,name);}greet(); //...
View ArticleAnswer by Avinash Maurya for typeof !== "undefined" vs. != null
(function(){ var a= b = 3; var ed = 103;})();//console.log(ed); //ed is not definedconsole.log("a defined? "+ (typeof a !== 'undefined')); //no defineconsole.log("b defined? "+ (typeof b !==...
View ArticleAnswer by JSpecs for typeof !== "undefined" vs. != null
I've actually come across if (typeof input !== 'undefined') in this scenario where it's being used to provide default function parameters: function greet(name, greeting) { name = (typeof name !==...
View ArticleAnswer by jNayden for typeof !== "undefined" vs. != null
good way:if(typeof neverDeclared == "undefined") //no errorsBut the best looking way is to check via :if(typeof neverDeclared === typeof undefined) //also no errors and no strings
View ArticleAnswer by Peeter for typeof !== "undefined" vs. != null
You shouldn't really worry about undefined being renamed. If someone renames undefined, you will be in a lot more trouble than just a few if checks failing. If you really want to protect your code,...
View ArticleAnswer by Claude for typeof !== "undefined" vs. != null
You can also use the void operator to obtain an undefined value:if (input !== void 0) { // do stuff }(And yes, as noted in another answer, this will throw an error if the variable was not declared, but...
View ArticleAnswer by Joey Adams for typeof !== "undefined" vs. != null
If the variable is declared (either with the var keyword, as a function argument, or as a global variable), I think the best way to do it is:if (my_variable === undefined)jQuery does it, so it's good...
View ArticleAnswer by UniquePhoton for typeof !== "undefined" vs. != null
if (input == undefined) { ... }works just fine. It is of course not a null comparison, but I usually find that if I need to distinguish between undefined and null, I actually rather need to distinguish...
View ArticleAnswer by Ivo Wetzel for typeof !== "undefined" vs. != null
If you are really worried about undefined being redefined, you can protect against this with some helper method like this:function is_undefined(value) { var undefined_check; // instantiate a new...
View ArticleAnswer by seanmonstar for typeof !== "undefined" vs. != null
typeof is safer as it allows the identifier to never have been declared before:if(typeof neverDeclared === "undefined") // no errorsif(neverDeclared === null) // throws ReferenceError: neverDeclared is...
View Articletypeof !== "undefined" vs. != null
I often see JavaScript code which checks for undefined parameters etc. this way:if (typeof input !== "undefined") { // do stuff}This seems kind of wasteful, since it involves both a type lookup and a...
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