检查未定义的变量在Chrome中不起作用

Question

I am checking if a variable is defined or not. It is working right in Firefox and when it comes to Chrome it is not working:

if(window[myClass] == undefined)
{
    return;
}

If the variable is not defined it should return.

I am using window[myClass] because I am taking name of the id from onclick event and using same named variable as id if variable is defined then else part should or if not defined then if part should work.

Answer 1

You should be doing something like this to check whether window[myclass] is defined or not:

if (typeof window[myclass] === 'undefined') {

But if I understand the question correctly, you might be looking to see if window[myclass] exists. Usually you do that like so:

if (window.hasOwnProperty(myclass)) {

Also, is myclass a variable or a string ( 'myclass' )?

Answer 2

From the last sentence in your question, sounds like myClass is actually ID of some element in your document.

In such case you should use such code to check if such element really exists:

if (!document.getElementById(myClass))
    return;

This will cancel the function when element with such ID does not exist.

Answer 3

if (typeof window[myClass] !== 'undefined') {
    //do stuff
} else {
    alert('undefined');
}