[英]Accessing JavaScript class variable inside a class function
I have this: 我有这个:
function FilterSelect(select, search) {
this.select = select;
this.search = search;
// Get the current list options
this.options = this.select.options;
// Whenever the text of the search box changes, do this
this.search.onkeyup = function() {
// Clear the list
while(this.select.options.length > 0) {
this.select.remove(0);
}
}
}
Inside of the onkeyup
function I would like to access select
, but I know it is not possible as is. 在
onkeyup
函数里面我想访问select
,但我知道它不可能存在。 What is the proper way to do this? 这样做的正确方法是什么?
Before the onkeyup function, declare a variable. 在onkeyup函数之前,声明一个变量。 Something like
var _this = this
and then in the keyup function, just use _this
instead of this
. 像
var _this = this
类的东西然后在keyup函数中,只需使用_this
而不是this
。
So your code will look something like: 所以你的代码看起来像:
var _this = this;
// Whenever the text of the search box changes, do this
this.search.onkeyup = function() {
// Clear the list
while(_this.select.options.length > 0) {
_this.select.remove(0);
}
}
You need to create a variable which will be held in the closure scope of the onkeyup
function: 您需要创建一个变量,该变量将保存在
onkeyup
函数的闭包范围内:
function FilterSelect(select, search) {
var _this = this; // <-- win
_this.select = select;
_this.search = search;
// Get the current list options
_this.options = this.select.options;
// Whenever the text of the search box changes, do this
_this.search.onkeyup = function() {
// Clear the list
while(this.select.options.length > 0) {
_this.select.remove(0);
}
}
}
By doing this, you ensure that the proper value will be referenced regardless of what scope the onkeyup
function is called with (usually the global/window scope because of eventing). 通过执行此操作,您可以确保将引用正确的值,而不管调用
onkeyup
函数的范围(通常是因为事件而导致的全局/窗口范围)。
EDIT 编辑
Actually, if you just need to access select
, you should be able to do this already: 实际上,如果你只需要访问
select
,你应该可以这样做:
this.search.onkeyup = function() {
// Clear the list
while(this.select.options.length > 0) {
select.remove(0);
}
}
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