Your question: Why does JavaScript Have null and undefined?

Why JavaScript have 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.

What is null and undefined in JavaScript?

Null: It is the intentional absence of the value. It is one of the primitive values of JavaScript. Undefined: It means the value does not exist in the compiler. It is the global object.

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.

Why is null an object in JavaScript?

The JavaScript specification says about null : null is a primitive value that represents the intentional absence of any object value. If you see null (either assigned to a variable or returned by a function), then at that place should have been an object, but for some reason, an object wasn’t created.

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Is null == undefined?

null is an assigned value. It means nothing. undefined means a variable has been declared but not defined yet.

What is the value of null == undefined in JavaScript?

Here as the variable is declared but not assigned to any value, the variable by default is assigned a value of undefined. On the other hand, null is an object. It can be assigned to a variable as a representation of no value. JavaScript never sets a value to null.

Is it better to 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.

What is better null or undefined?

Use null for set a variable you know it is an Object. Use undefined for set a variable whose type is mixed.

Should I return null or undefined?

Undefined typically refers to something which has not yet been assigned a value (yet). Null refers to something which definitively has no value. In that case, I would recommend returning a null. Note that a function with no specified return value implicitly returns undefined.

Is null undefined JavaScript?

Summary. null is an assigned value. It means nothing. undefined typically means a variable has been declared but not defined yet.

IS NULL check JavaScript?

Javascript null is a primitive type that has one value null. JavaScript uses the null value to represent a missing object. Use the strict equality operator ( === ) to check if a value is null . The typeof null returns ‘object’ , which is historical bug in JavaScript that may never be fixed.

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What is == and === in JavaScript?

= is used for assigning values to a variable in JavaScript. == is used for comparison between two variables irrespective of the datatype of variable. === is used for comparision between two variables but this will check strict type, which means it will check datatype and compare two values.

Is NaN in JavaScript?

JavaScript Number isNaN()

isNaN() method determines whether a value is NaN (Not-A-Number). This method returns true if the value is of the type Number, and equates to NaN. Otherwise it returns false. … isNaN() does not convert the values to a Number, and will not return true for any value that is not of the type Number.

What is null 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.

Is null false in Java?

In Java, null is a keyword much like the other keywords public, static or final. It is just a value that shows that the object is referring to nothing. … When you declare a boolean variable, it gets its default value as false. Similarly, any reference variable in Java has null as a default value.