What is the difference between undefined value and null value?

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Undefined value cannot be explicitly stated that is there is no keyword called undefined whereas null value has keyword called null.

typeof undefined variable or property returns undefined whereas typeof null value returns object

2008-11-25, 4578👍, 0💬

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What does undefined value mean in JavaScript?
What does undefined value mean in JavaScript? Undefined value means the variable used in the code doesn't exist or is not assigned any value, or the property doesnt exist. 2008-11-18, 5149👍, 0💬

What is variable typing in JavaScript?
What is variable typing in JavaScript? It is perfectly legal to assign a number to a variable and then assign a string to the same variable as in the following example: i = 10; i = "string"; This is called variable typing 2008-11-25, 4885👍, 0💬

How to select an element by id and swapping an image?
How to select an element by id and swapping an image? ... <script language="JavaScript" type="text/javascript" > function setBeerIcon() { var beerIcon = document.getElementById("beerI con");beerIcon.src = "images/"+getSelectValue("beer ")+".jpg";} </script> ... <img border="0" s... 2008-11-18, 4881👍, 0💬

To set all checkboxes to true using JavaScript?
To set all checkboxes to true using JavaScript? //select all input tags function SelectAll() { var checkboxes = document.getElementsByTagName( "input");for(i=0;i<checkboxes.le ngth;i++){ if(checkboxes.item(i).attribut es["type"].value== "checkbox") { checkboxes.item(i).checked = true; } } } 2008-11-11, 4859👍, 0💬

You have an ASP.NET web application running on a web-farm ...
You have an ASP.NET web application running on a web-farm that does not use sticky sessions - so the requests for a session are not guaranteed to be served the same machine. Occasionally, the users get error message Validation of viewstate MAC failed. What could be one reason that is causing this er... 2008-11-11, 4794👍, 0💬

What are undefined and undeclared variables?
What are undefined and undeclared variables? Undeclared variables are those that are not declared in the program (do not exist at all), trying to read their values gives runtime error. But if undeclared variables are assigned then implicit declaration is done . Undefined variables are those that are... 2008-12-02, 4656👍, 0💬

What is === operator?
What is === operator? ==== is strict equality operator, it returns true only when the two operands are having the same value without any type conversion. 2008-12-09, 4646👍, 0💬

What is the difference between undefined value and null value?
What is the difference between undefined value and null value? Undefined value cannot be explicitly stated that is there is no keyword called undefined whereas null value has keyword called null. typeof undefined variable or property returns undefined whereas typeof null value returns object 2008-11-25, 4579👍, 0💬

Does JavaScript have the concept level scope?
Does JavaScript have the concept level scope? No. JavaScript does not have block level scope, all the variables declared inside a function possess the same level of scope unlike c, c++, and java. 2008-12-02, 4509👍, 0💬

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