What is the correct way to check if a global variable exists?

Question

JSLint is not passing this as a valid code:

/* global someVar: false */
if (typeof someVar === \"undefined\") {
    var someVar = \"hi!\";
}

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Answer 1

if (typeof someVar === "undefined") {
    var someVar = "hi!";
}

will check if someVar (local or global) is undefined.

If you want to check for a global variable you can use

if(window['someVar'] === undefined) {
    ...
}

assuming this is in a browser :)