typeof [(]expression[)]

As you can see, the parentheses are optional, because typeof is an operator, not a function. It returns one of the following strings:

• "boolean"
• "function"
• "number"
• "object"
• "string"
• "undefined"

function doIt() {
  // do something
}

var a = true;
var b = doIt;
var c = 19;
var d = window.location;
var e = "Microsoft";
var f;
alert(typeof a); // "boolean"
alert(typeof b); // "function"
alert(typeof c); // "number"
alert(typeof d); // "object"
alert(typeof e); // "string"
alert(typeof f); // "undefined"

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