jquery - Checking something isEmpty in Javascript?

Question

How can I check if a variable is empty in Javascript? Sorry for the stupid question, but I'm a newbie in Javascript!

if(response.photo) is empty {
    do something
else {
    do something else
}

response.photo was from JSON, and it could be empty sometimes, empty data cells! I want to check if it's empty.

Answer 1

If you're testing for an empty string:

if(myVar === ''){ // do stuff };

If you're checking for a variable that has been declared, but not defined:

if(myVar === null){ // do stuff };

If you're checking for a variable that may not be defined:

if(myVar === undefined){ // do stuff };

If you're checking both i.e, either variable is null or undefined:

if(myVar == null){ // do stuff };