JavaScript 1.0, JScript 2.0; deprecated by ECMAScript
function.caller
In early versions of JavaScript, the caller property of a Function object is a reference to the function that invoked the current one. If the function was invoked from the top level of a JavaScript program, caller is null. This property may only be used from within the function (i.e., the caller property is only defined for a function while that function is executing).
Function.caller is not part of the ECMAScript standard and is not required in conforming implementations. It should not be used.