如何以编程方式检测对象是否为jQuery对象?例如:
// 1. declare some variables
var vars = [1, 'hello', ['bye', 3], $(body), { say: 'hi' }];
// 2. ??? : implement function that tests whether its parameter is a jQuery object
function isjQuery(arg) { /* ??? */ }
// 3. profit
var test = $.map(vars, isjQuery); /* expected [ false, false, false, true, false ] */