如何在变量中缓存HTMLElement.focus？

Question

将HTMLElement的focus函数存储在变量中的正确上下文是什么？

我试过了，

var elem = document.getElementById('elem');
var focus = elem.focus.bind(document); // focus() Illegal Invocation
var focus2 = elem.focus.bind(elem); // focus2() Illegal Invocation

Answer 1

将其包装到您自己的功能中：

var elem = document.getElementById('elem');
var focusElem = function(){ elem.focus(); };
focusElem();