访问全局变量的匿名函数——这怎么可能？

Question

当我 setInterval 设置如下时：

var intervalTime = 200;
var i = 0;
var elements = document.getElementsByTagName('elements');
var elementsLength = elements.length;

var enterElements = setInterval(function(){

    elements[i].style.transform = 'translate(0,0)';
    i++;

    if (i > (elementsLength - 1)) {
        clearInterval(enterElements);
    }

    },intervalTime);

有效！

但我认为 functions 有作用域？

我理解intervalTime应该解析正确，但是setInterval()里面的匿名函数怎么访问

elements
i
elementsLength

我知道当我编写命名函数时，该函数无法访问在其外部声明的变量。

匿名函数与命名函数不同吗？

Answer 1

I know that when I write a named function, that function cannot then access variables declared outside of itself.

你怎么知道的？见 MDN:

However, a function can access all variables and functions defined inside the scope in which it is defined. In other words, a function defined in the global scope can access all variables defined in the global scope. A function defined inside another function can also access all variables defined in its parent function and any other variable to which the parent function has access.

访问全局变量的匿名函数——这怎么可能？

Anonymous function accessing global variable - how is this even possible?

javascript

scope

anonymous-function