Why JavaScript has both null and undefined?

2 Answers. The value null represents the intentional absence of any object value. You also get undefined when you call a non-existent property or method of an object.

Why do we need undefined in JavaScript?

Undefined is also a primitive value in JavaScript. A variable or an object has an undefined value when no value is assigned before using it. So you can say that undefined means lack of value or unknown value. In the above example, we have not assigned any value to a variable named ‘myVar’.

Should I use null or undefined JavaScript?

Only use null if you explicitly want to denote the value of a variable as having “no value”. As @com2gz states: null is used to define something programmatically empty. undefined is meant to say that the reference is not existing. A null value has a defined reference to “nothing”.

Does JavaScript support null?

What is null in JavaScript. JavaScript null is a primitive type that contains a special value null . JavaScript uses the null value to represent the intentional absence of any object value. If you find a variable or a function that returns null , it means that the expected object couldn’t be created.

What does JavaScript use instead of == and !=?

What does javascript use instead of == and !=? Explanation: The subset does not include the comma operator, the bitwise operators, or the ++ and — operators. It also disallows == and != because of the type conversion they perform, requiring use of === and !==

Why NULL is object in JavaScript?

The value null represents the intentional absence of any object value. It is one of JavaScript’s primitive values and is treated as falsy for boolean operations. y is declared but not defined. It is declared with no value so it is undefined.

What is the relationship between null and undefined?

null is a special value meaning “no value”. null is a special object because typeof null returns ‘object’. On the other hand, undefined means that the variable has not been declared, or has not been given a value.

Why null == undefined is true in JavaScript?

null and undefined both return false . That’s why your code is actually checking if false is equal to false . However their types are not equal. Because of that, the next statement will return false, as the === comparison operator checks both the types and their value.

What is definition of an undefined value in JavaScript?

The undefined property indicates that a variable has not been assigned a value, or not declared at all.

What does JavaScript use instead == and !=?

Is null equal to undefined in JavaScript?

As you can see so far, null and undefined are different, but share some similarities. Thus, it makes sense that null does not strictly equal undefined. But, and this may surprise you, null loosely equals undefined. In JavaScript, a double equals tests for loose equality and preforms type coercion.

What does the null value mean in JavaScript?

The null value is a primitive value that represents the null, empty, or non-existent reference. When you declare a variable through var and do not give it a value, it will have the value undefined. By itself, if you try to WScript.Echo () or alert () this value, you won’t see anything.

Is there a way to deal with null or undefined values?

There are a couple of features that can help you deal with null or undefined values. Both are stage 3 proposals at the time of this writing, but if you’re reading from the future, you may be able to use them. As of this writing, optional chaining is a stage 3 proposal.

What is an undefined variable in JavaScript?

When you declare a variable in javascript, it is assigned the value undefined. This means the variable is untouched and can be assigned any value in future. It also implies that you don’t know the value that this variable is going to hold at the time of declaration.