javascript test for existence of nested object key -

if have reference object -

var test = {}; 

that potentially (but not immediately) have nested objects, -

{ level1:{level2:{level3:'level3'}} }; 

what best way test existence of keys in nested objects?

this -

alert(test.level1); 

returns 'undefined', -

alert(test.level1.level2.level3); 

fails.

i'm doing -

if(test.level1 && test.level1.level2 && test.level1.level2.level3) {     alert(test.level1.level2.level3); } 

but wondering if there's better way.

you have step step if don't want typeerror, because if 1 of members null or undefined, , try access member exception thrown.

you can either catch exception, or make function test existence of multiple levels, this:

function checknested(obj /*, level1, level2, ... leveln*/) {   var args = array.prototype.slice.call(arguments, 1);    (var = 0; < args.length; i++) {     if (!obj || !obj.hasownproperty(args[i])) {       return false;     }     obj = obj[args[i]];   }   return true; }  var test = {level1:{level2:{level3:'level3'}} };  checknested(test, 'level1', 'level2', 'level3'); // true checknested(test, 'level1', 'level2', 'foo'); // false