Question

I have a piece of code that goes like this. This piece of code works but it looks horrible.

if(typeof(d.object) != "undefined"){
  if(typeof(d.object.property) != "undefined"){
    if(typeof(d.object.property.length) != "undefined"){
      // do the code
    }
    else alert("error");
  }
  else alert("error");
}
else alert("error");

Is there any way this can be rewritten so it does the same but more efficient. Especially because the errors are all the same.

Answer 1

Supposing you’re not interested in the property if its length is null or 0 (or more generally “falsy” as suggested by Jan Dvorak), then you might make it a little more readable even without using try/catch :

if (d && d.object && d.object.property && d.object.property.length){

} else {
   alert('error');
}

in most cases this is the way to go.

About the “falsy”, from the MDN :

Any value that is not undefined, null, 0, NaN, or the empty string
(“”), and any object, including a Boolean object whose value is false,
evaluates to true when passed to a conditional statement