Is undefined a JavaScript keyword?

undefined is not a JavaScript keyword, it is a property of global object, i.e., it is a variable in global scope.

You can shadow the global property undefined in local scope.

HelloWorld.js

function print_me () {
    console.log(undefined)
    var undefined = "shadowed";
    console.log(undefined);
}

print_me();

Output

undefined

shadowed

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