This question already has answers here:
$watch an object
(8 answers)
Closed 7 years ago.
I have a Complex scope variable, something like the following.
$scope.ComplexVariable={
PrimaryObjOne:{
SecondaryOne:'',
SecondaryTwo:''
},
PrimaryObjTwo:{
SecondaryOne:'',
SecondaryTwo:''
}
}
Is there any clean way to check if any of the properties(at the secondary level in my example) associated with this object were modified. Adding a $watch against each property would work, but I was wondering if there was a cleaner way to do this.
$scope.$watch("ComplexVariable", function (oldVal, newVal) {
}, true);
The true at the end will watch the entire object for any changes.
The third argument to $scope.$watch allows you to compare objects using object equality rather than reference equality (which is the default).
function objectChanged() {
// ...
}
var useObjectEquality = true;
$scope.$watch('ComplexVariable', objectChanged, useObjectEquality);
This makes use of angular.equals rather than == or ===.
Related
This question already has answers here:
Self-references in object literals / initializers
(30 answers)
Closed 5 years ago.
In a simple JS object like this:
var LeadserData = {
agent_id: 2,
object_queries: {
emails: {
url: "/manual_emails/",
method: 'GET',
send_data: {
the_id: this.agent_id
}
}
}
}
it is obviously possible to access the agent_id simply like this:
LeadserData.agent_id = 100;
alert(LeadserData.agent_id);
This obviously returns 100. But why does not the internal reference of this.agent_id work?
alert((LeadserData.object_queries.emails.send_data.the_id));
I was expecting this to come out as "100" as well, but instead it is undefined. The whole fiddle is here: https://jsfiddle.net/h88zc5nw/1/
What is the explanation for this behaviour, and how can I tweak this to return the expected 100.
First of all, you are using an object literal. You can't use this inside an object literal, at least it won't be what you think it is. It will be whatever this available while the object literal is constructed.
Second, even if we assume that the above works, numbers are native types, they won't be shared via their references. So changing LeadserData.agent_id won't affect LeadserData.object_queries.emails.send_data.the_id even if you have assigned one to the other. Native types are copied on assignment, not passed around using a reference (like you would do with an object).
This question already has answers here:
How do I correctly clone a JavaScript object?
(81 answers)
Closed 5 years ago.
Let's say we got this:
this.myObject = {"id":1};
and we want to store the state of my object as my object original as the following:
this.myObjectORG = this.myObject;
then you go on your business and change props on your object like this
this.myObject.id = 2;
and to your surprise down the road, you realize that
console.log (this.myObjectORG.id) // also reports 2
Well, that's just how JS works & I'm not questioning that.
Is there a way to preserve the state of the myObject so I can do comparisons whether its properties changed since its original state?
At some point I'd like to be able to do something like this
if ( this.myObjectORG.id !== this.myObject.id ) {
// but this condition is never true
}
Does this help:-
An Object.assign method is part of the ECMAScript 2015 (ES6) standard and does exactly what you need.
var this.myObjectORG = Object.assign({}, this.myObject);
The Object.assign() method is used to copy the values of all enumerable own properties from one or more source objects to a target object.
This question already has answers here:
Does node.js have equivalent to window object in browser
(2 answers)
Closed 6 years ago.
I know with browser-run JavaScript, I could use window[varName]=value; to set global variables. I seem to remember there being a function to accomplish this in Node JS, but I'm not sure what it is.
If it helps, I'm aiming to set all the properties of an object as separate own variables.
In Node.js the global variables are stored in the global object, I think...
Then it'd be so:
global[varName] = value;
// or...
global.varName = value;
I think you're confusing something. Maybe you want to initialize a object constructor expression.
{ property: "string, or anything else" }
// this expression returns a object that can be assigned
// everywhere, but when assigned, turns a reference
If you want to get/set properties in this object you must do the same thing you were doing before, index the object with the keys [...] or ., then you can optionally assign (set) the object's property with =, else it'll be returned.
This question already has answers here:
JavaScript by reference vs. by value [duplicate]
(4 answers)
Closed 8 years ago.
I have a question about referencing objects in javascript.
Say I have a variable that is some object (lets say json) and it is called objOne - (var objOne = someJSONObject;).
If I go ahead and declare
var objTwo = objOne;
will I have two references to the same Object? Kind of like a c pointer?
To sum it up :
assignements are done by value
you never manipulate objects, only object references
This means that
you'll have two references to the same object (you can check that by changing a property of the object)
when you're passed in a variable the value of a primitive, changing your variable doesn't change other variables
EDIT : as it's a duplicate I'll delete this answer in a minute to allow a proper closing if there's no other answer. Please vote to close.
Yes, objects are passed by reference:
function changeVal(obj){
obj.value = "bar"
}
(function checkRefs(){
var myObject = {
value: "foo"
};
alert(myObject.value);
changeVal(myObject);
alert(myObject.value);
})();
This question already has answers here:
Add a property to a JavaScript object using a variable as the name? [duplicate]
(14 answers)
Closed 9 years ago.
In JavaScript I am trying to update an object value through a function, through which I am passing the object property to update.
However, this won't work - and I can see why, but don't know how to combat it!
myObject = {"testItem": "testValue"};
console.log(myObject.testItem);
function updateSomeValue(objectItem, newValue){
myObject.objectItem = newValue;
}
updateSomeValue('testItem', 'newValue');
console.log(myObject.testItem);
Now, I can see the issue here is that in the function, myObject.objectItem is expecting an item in the object called objectItem - it won't translate it to testItem.
How do I do this?
By using a different notation. Using [ .. ] you can specify the property name as a string.
function updateSomeValue(objectItem, newValue){
myObject[objectItem] = newValue;
}