Javascript检查未定义或空的对象/变量

Posted 2021-02-26

Based on some comments in [StackOverflow Question](http://stackoverflow.com/questions/95875/javascript-check-to-see-if-a-variable-is-an-object "How to check if a variable is an object")

if(typeof(foo) !== 'undefined' && foo != null) {
    //you can use foo!
}