原来JavaScript的闭包概念是这样的

JavaScript functions are a combination of code to be executed and the scope in which to execute them. This combination of code and scope is known as a closure in the computer science literature. All JavaScript functions are closures. These closures are only interesting, however, in the case discussed above: when a nested function is exported outside the scope in which it is defined. When a nested function is used in this way, it is often explicitly called a closure.