内部函数作用域的访问元素，而不是敲除中的外部元素

Question

I have my code below. I have var viewData in my constructor appVM as null and in activate I am filling it with some value. Now I have to use activate scope of viewData instead of outer scope. what my self var of Lis should be assign with for the same.

var appVM = function () {        
    this.viewData = null;
    this.subscription = ko.observable();      

    this.activate = function (viewActivationData) {
        var self = this;
        self.viewData = viewActivationData.viewData;
    };

appVM.prototype.list = function () {
    var self = this;
    getEmpLists(self.viewData.empId);
};

Answer 1

You'll want to do a search for tutorials about how closures work in JavaScript.

Here are a couple of ways to solve your issue:

First: (Creates a closure for 'this')

var appVM = function () {        
    var self = this;
    this.viewData = null;
    this.subscription = ko.observable();      

    this.activate = function (viewActivationData) {
        self.viewData = viewActivationData.viewData;
    };

    appVM.prototype.list = function () {
        getEmpLists(self.viewData.empId);
    };
}

Second: (Avoids the need for a closure)

var appVM = function() {
  var viewData = null;
  var subscription = ko.observable();

  var activate = function(viewActivationData) {
    viewData = viewActivationData.viewData;
  };

  var list = function() {
    getEmpLists(viewData.empId);
  };

  return {
    viewData: viewData,
    subscription: subscription,
    activate: activate,
    list: list,
  };
}

These are just two simple example. There are other ways you could solve this, but these are probably the most simple. Ultimately you'll need to use several different techniques when controlling and understanding 'this'.