将可观察变量设为null

Question

I have a an observable variable of the following format:

var obvar = ko.observable("");

obvar({view:'dummy.html',model:'dummymodel'});

In one of my checks I want to empty the contents , if variable "obvar" contains

{view:'dummy.html',model:'dummymodel'}.

I tried obvar(""); but its not happening. obvar =""; would convert it to normal string. How to empty the contents?

Answer 1

Your first code snippet:

 var obvar = ko.observable(""); obvar({view:'dummy.html',model:'dummymodel'}); 

has a special but important feature. The obvar observable first contains a string , and after the second line it contains an Object .

Your requirement that you mention is (emphasis mine):

...I want to empty the contents , if variable obvar contains {view:'dummy.html',model:'dummymodel'}

It's unclear to me what you mean by "empty" the contents, and perhaps to you as well (since you've tried obvar(""); , which in a sense "empties" the content, but it had not the desired result).

At any rate, here are two ways to do it, in a runnable snippet so you can see proof that it's working:

 function ViewModel() { var self = this; var obvar = ko.observable(""); obvar({view:'dummy.html',model:'dummymodel'}); self.obvar = obvar; // Expose it so the view can demo the workings. function canEmptyContents() { // empty the contents if variable "obvar" contains {view:'dummy.html',model:'dummymodel'} return obvar().view === 'dummy.html' && obvar().model === 'dummymodel'; } self.option1 = function() { if (canEmptyContents()) { obvar(""); } }; self.option2 = function() { if (canEmptyContents()) { obvar({ dummy: "", model: "" }); } }; } ko.applyBindings(new ViewModel()); 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/2.3.0/knockout-min.js"></script> <button data-bind="click: option1">Option 1: empty with string</button> <button data-bind="click: option2">Option 2: empty with empty object</button> <hr> Debug info: <pre data-bind="text: ko.toJSON($root, null, 2)"></pre>