When you are in JavaScript mode it is common for you to use
typeof operator to see whether a given variable, object, function etc. is known to JavaScript.
However, many times I find myself writing more complex code because it is a child of a child object that I need to check for a value. This makes for ugly code.
Being rather simple minded I chose to Google for an obvious solution. Unfortunately, nothing was immediately available (or I might be simple missing it). Most people seem to only need to be dealing with the top level object deceleration and, thus, no need for anything else.
So, to make a long story short, I created a simple helper function that does most of the work for me and cleans up the repetitive code. Feel free to use it at your leisure:
/**
* Take string input in varName and determine whether it is defined object in Javascript
* @param {String} varName
* @return {boolean}
* @author Bilal Soylu
*/
function isDefined(varName) {
var retStatus = false;
if (typeof varName == "string") {
try {
var arrCheck = varName.split(".");
var strCheckName = "";
for (var i=0; i < arrCheck.length; i++){
strCheckName = strCheckName + arrCheck[i];
//check wether this exist
if (typeof eval(strCheckName) == "undefined") {
//stop processing
retStatus = false;
break;
} else {
//continue checking next node
retStatus = true;
strCheckName = strCheckName + ".";
}
}
} catch (e) {
//any error means this var is not defined
retStatus = false;
}
} else {
throw "the varName input must be a string like myVar.someNode.anotherNode[]";
}
return retStatus;
}
Cheers,
-B.
