This is the code I am testing --
Works fine
document.write( 1 && undefined ); // prints undefined
document.write( 1 && 3 ); // prints 3
document.write( 1 && true ); // prints true
Throws error
document.write( 1 && NULL ); // throws Error
why using NULL throws arror although its working even for undefined
although i tested typeof NULL and its giving undefined but still its not working.let me know about this. (New to OOP programming)
NULL does not exist, try this
try {
document.write( 1 && NULL );
} catch ( e) {
document.write( 1 && null );
}
NULL is undefined because it doesn't exist. You're thinking of null.
document.write(1 && null); outputs null.
NULL does not exist in JavaScript because it's case-sensitive. It must be null.
It's null (lowercase), not NULL (uppercase)
Because undefined is different to a symbol that doesn't exist, the browser is throwing an error. From the Chrome console:
> 1 && null
null
> 1 && NULL
ReferenceError: NULL is not defined
> NULL
ReferenceError: NULL is not defined
read this may be it will answer your question JavaScript undefined vs. null
Using typeof something only gives the type of that expression; it's undefined in this case and so using that symbol naturally gives an error. It's the same as:
typeof unknownvar
// "undefined"
unknownvar
// ReferenceError: unknownvar is not defined
The exception is the symbol undefined itself:
typeof undefined
// "undefined"
undefined
// undefined
In your particular case, NULL should be null.
var NULL = null;