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

try

variableName in window

or

typeof window[variableName] != 'undefined'

or

window[variableName] !== undefined

or

window.hasOwnProperty(variableName)