How to check if a variable is null or empty string or all whitespace in JavaScript?

Question

I need to check to see if a variable is null or has all empty spaces or is just blank (\"\").

I have the following, but it is not working:

var addr;
         


        

Answer 1

if (addr == null || addr.trim() === ''){
  //...
}

A null comparison will also catch undefined. If you want false to pass too, use !addr. For backwards browser compatibility swap addr.trim() for $.trim(addr).