Sorry for the question but I am new to JavaScript
i have defined an object
define(['sharedServices/pubsub', 'sharedServices/topics'], function (pubsub,topics) {
'use strict';
function Incident() {
var that = this;
this._dtasks = [];
this.handlePropertyGet = function(enstate, ename) {
if (!this.entityAspect || !this.entityAspect.entityManager || !this.entityAspect.entityManager.isReady) {
enstate = [];
} else {
enstate = this.entityAspect.entityManager.executeQueryLocally(new breeze.EntityQuery(ename).where('IncidentID', 'eq', this.IncidentID));
}
return enstate;
};
Object.defineProperty(this, 'DTasks', {
get: function () {
return this.handlePropertyGet(this._dtasks, "DTasks");
},
set: function (value) { //used only when loading incidents from the server
that.handlePropertySet('DTask', value);
},
enumerable: true
});
}
return {
Incident: Incident
};
});
when I am calling the property DTasks the inner member _dtask is equal to [], even when i enter the get property and i see that the enstate is filled with the objects when the handlePropertyGet is finished and returned to the get scope the _dtasks remains empty, doesn't it supposed to pass as reference?
this._dtasks "points" to an array. If you pass it as a parameter to this.handlePropertyGet, you make enstate refer to the same array.
If you change the array (as in enstate.push("bar")), the change affects this._dtasks too: you are actually changing neither of them, just the array they both point to.
However, the lines
enstate = []
and
enstate = this.entityAspect.entityManager.executeQueryLocally(new breeze.EntityQuery(ename).where('IncidentID', 'eq', this.IncidentID));
don't modify the array you already have. Instead, they create new arrays and change enstate so that it points to them. this._dtasks, however, remains unchanged.
An easy way to fix it would be to change the code inside the getter to
return this.handlePropertyGet("_dtasks", "DTasks");
and handlePropertyGet to
this.handlePropertyGet = function(enstate, ename) {
if (!this.entityAspect || !this.entityAspect.entityManager || !this.entityAspect.entityManager.isReady) {
this[enstate] = [];
} else {
this[enstate] = this.entityAspect.entityManager.executeQueryLocally(new breeze.EntityQuery(ename).where('IncidentID', 'eq', this.IncidentID));
}
return this[enstate];
};
That way, you would be changing the value of this._dtasks directly.
As an alternative, you could achieve the same result by changing enstate = [] to enstate.length = 0 (which clears the array instead of changing the variable. See https://stackoverflow.com/a/1232046/3191224) and enstate = this.entityAspect.[...] to
var newContent = enstate = this.entityAspect.entityManager.executeQueryLocally(new breeze.EntityQuery(ename).where('IncidentID', 'eq', this.IncidentID));
enstate.length = 0;
Array.prototype.push.apply(enstate, newContent);
which clears the array and then pushes all the elements from the other array, effectively replacing the whole content without changing enstate itself.
My guess is that you are trying to do something like this
Javascript
function Incident() {
var reset = false;
this._dtasks = [];
this.handlePropertyGet = function (ename) {
if (reset) {
this._dtasks = [];
} else {
this._dtasks = [1, 2, 3];
}
return this._dtasks;
};
Object.defineProperty(this, 'DTasks', {
get: function () {
return this.handlePropertyGet("DTasks");
},
enumerable: true
});
}
var x = new Incident();
console.log(x.DTasks);
Output
[1, 2, 3]
On jsFiddle
So you can then use this simplified example with the ideas given by #user3191224
Related
So I've been trying to find a solution to this for a little while with no luck.
const nameTest = 'testName';
const test = {
RANDOM_ONE: {
NAME: 'testName',
SOMETHING: {...}
},
RANDOM_TWO: {
NAME: 'Name',
SOMETHING: {...}
}
}
Is there any simple, easy way where I can compare the nameTest and the NAME key without knowing what the RANDOM_X is in order to access NAME?
You can use Object.keys() to get the array of all the keys. Then loop through the array to check the property:
const nameTest = 'testName';
const test = {
RANDOM_ONE: {
NAME: 'testName',
SOMETHING: {}
},
RANDOM_TWO: {
NAME: 'Name',
SOMETHING: {}
}
}
let testKeys = Object.keys(test);
testKeys.forEach(function(k){
console.log(test[k].NAME == nameTest);
});
You can use a for ... in loop:
for (let key in test) {
if (test[key].NAME === nameTest) {
// do something
}
}
I hope we know that 2 levels down into test is your object. You could write a function, to compare the name key.
function compare(obj, text){
for(let x in obj){
if(obj.x.name == text) return true;
else ;
}
}
Then call the function with your object and the string.
let a = compare(test, nameTest);
Note: this would compare the object to only ascertain if it contains the nameTest string.
var obj= test.filter(el){
if(el.NAME==nameTest)
{
return el;
}
}
var x= obj!=null?true:false;
You could use find.
The find method executes the callback function once for each index of
the array until it finds one where callback returns a true value. If
such an element is found, find immediately returns the value of that
element. Otherwise, find returns undefined.
So it is more memory efficient, than looping over the whole object with forEach, because find returns immediately if the callback function finds the value. Breaking the loop of forEach is impossible. In the documentation:
There is no way to stop or break a forEach() loop other than by
throwing an exception. If you need such behavior, the forEach() method
is the wrong tool.
1. If you want to get the whole object
var nameTest = 'testName';
var test = {
RANDOM_ONE: {
NAME: 'testName',
SOMETHING: {}
},
RANDOM_TWO: {
NAME: 'Name',
SOMETHING: {}
}
};
function getObjectByNameProperty(object, property) {
var objectKey = Object.keys(object)
.find(key => object[key].NAME === property);
return object[objectKey];
}
var object = getObjectByNameProperty(test, nameTest);
console.log(object);
2. If you just want to test if the object has the given name value
var nameTest = 'testName';
var test = {
RANDOM_ONE: {
NAME: 'testName',
SOMETHING: {}
},
RANDOM_TWO: {
NAME: 'Name',
SOMETHING: {}
}
};
function doesObjectHaveGivenName(object, nameValue) {
var objectKey = Object.keys(object)
.find(key => object[key].NAME === nameValue);
return objectKey ? true : false;
}
console.log( doesObjectHaveGivenName(test, nameTest) );
I have some code like this
$scope.grabItems = function(data) {
data.model = ['test'];
console.log($scope.ui.projects);
}
$scope.ui.projects = [];
$scope.grabProjects = function() {
$scope.grabItems({model: $scope.ui.projects});
}
I'm trying to change the $scope.ui.projects variable using the parameter of another function (this is so that I can write an abstract grabItems function using any variable).
The problem is it looks like the data.model = ['test'] isn't changing the $scope.ui.projects variable at all but is creating a brand new variable.
How would I modify the outer variable in a reusable way like this?
Note that $scope.ui.projects could potentially be any variable.
You are not actually not changing $scope.ui.projects, Try like this
$scope.grabItems = function(data) {
data.model = ['test'];
console.log($scope.ui.projects);
}
$scope.ui.projects = [];
$scope.grabProjects = function() {
$scope.grabItems($scope.ui.projects);
}
If it's not clear, share what is your expected object.
You could achieve it by pushing items into the array:
$scope.grabItems = function(data) {
if(!angular.isArray(data.model))
throw new Error('Array expected');
data.model.length = 0; // empty array
data.model.push('test'); // push items
console.log($scope.ui.projects);
}
$scope.ui.projects = [];
$scope.grabProjects = function() {
$scope.grabItems({model: $scope.ui.projects});
}
I have a function like this :
$scope.saveSearch = function () {
var alreadyExist = false;
for (var i = 0; i < $scope.savedSearch.length; i++) {
if (JSON.stringify($scope.searched) === JSON.stringify($scope.savedSearch[i])) {
alreadyExist = true;
break;
}
}
if (!alreadyExist) {
$scope.savedSearch.push($scope.searched);
localStorage.setItem("savedSearch", JSON.stringify($scope.savedSearch));
}
};
Before that : $scope.savedSearch = [];
$scope.searched = {
IS: "",
area: "",
block: "",
type: "",
level: ""
};
The values in $scope.searched object are initialized and then modified by the user.
My problem is :
$scope.savedSearch always contains only the last pushed object. Instead of adding the object to the array, it just replaces the current object.
I don't understand why.
You'll want to change your push line to:
$scope.savedSearch.push(angular.copy($scope.searched));
I believe your problem is that objects are passed by reference. Since the object you have in the savedSearch is always pointing to the exact object you're searching, alreadyExist will always be true.
My guess is that the object reference is being stored in your array, not the actual object itself. Because of this, any subsequent calls to push the object to your array will not work because the object reference already exists in the array. It's merely updated.
Try this instead. Use angular.copy() to create a deep copy of the object and push the copy to your array. See if that works.
if (!alreadyExist) {
$scope.savedSearch.push(angular.copy($scope.searched));
localStorage.setItem("savedSearch", JSON.stringify($scope.savedSearch));
}
You are pushing the Object outside of the for so only 1 element get pushed in try move it inside the for and every object which doesnt already exist will be pushed in
$scope.saveSearch = function () {
var alreadyExist = false;
for (var i = 0; i < $scope.savedSearch.length; i++) {
if (JSON.stringify($scope.searched) === JSON.stringify($scope.savedSearch[i])) {
alreadyExist = true;
break;
}
if (!alreadyExist) {
$scope.savedSearch.push($scope.searched);
localStorage.setItem("savedSearch", JSON.stringify($scope.savedSearch));
}
}
};
easier way would be to just
$scope.saveSearch = function () {
var alreadyExist = false;
for (var i = 0; i < $scope.savedSearch.length; i++) {
if (JSON.stringify($scope.searched) != JSON.stringify($scope.savedSearch[i])) {
$scope.savedSearch.push($scope.searched);
localStorage.setItem("savedSearch", JSON.stringify($scope.savedSearch));
}else{
break
}
}
};
How do I grant access to inner properties of objects in the right way? This is what does break my application:
I have an object that handles an array (simplified here):
function ListManager() {
var list = [],
add = function (element) {
list.push(element);
},
clear = function () {
list = [];
};
return {
add: add,
clear: clear,
list : list
};
};
But I get this when using it:
var manager = new ListManager();
manager.add("something");
manager.clear();
console.log(manager.list.length); // <= outputs "1"!
Stepping through the code shows, that within the clear method, list becomes a new array. But from outside the ListManager the list ist not cleared.
What am I doing wrong?
This is because clear sets the value of var list, not the .list on the object returned from ListManager(). You can use this instead:
function ListManager() {
var list = [],
add = function (element) {
this.list.push(element);
},
clear = function () {
this.list = [];
};
return {
add: add,
clear: clear,
list : list
};
}
Using your current structure, you could do:
function ListManager() {
var list = [],
add = function (element) {
list.push(element);
},
clear = function () {
list = [];
};
getList=function(){
return list;
}
return {
add: add,
clear: clear,
list : list,
getList: getList
};
};
var manager = new ListManager();
manager.add("something");
console.log(manager.getList()); // ["something"]
manager.clear();
console.log(manager.getList()); // []
function ListManager() {
var list = [],
add = function (element) {
this.list.push(element);
},
clear = function () {
this.list = [];
};
return {
add: add,
clear: clear,
list : list
};
};
var manager = new ListManager();
manager.add("something");
manager.clear();
console.log(manager.list.length); // <= now outputs "0"!
As has already been explained, your issue is that when you do list = [], you are changing the local variable list, but you aren't changing this.list as they are two separate variables. They initially refer to the same array so if you modified the array rather than assigning a new one to just one of the variables, they would both see the change.
Personally, I think you're using the wrong design pattern for creating this object that just makes things more complicated and makes it more likely you will create problems like you did. That design pattern can be useful if you want to maintain private instance variables that are not accessible to the outside world, but it creates a more complicated definition and maintenance if everything is intended to be public.
One of my programming goals is to use the simplest, cleanest way of expressing the desired functionality.
So that end, since everything in this object is intended to be public and accessible from outside the object, this is a whole lot simpler and not subject to any of the types of problems you just had:
function ListManager() {
this.list = [];
this.add = function(element) {
this.list.push(element);
}
this.clear = function() {
this.list = [];
}
}
Or, perhaps even use the prototype:
function ListManager() {
this.list = [];
}
ListManager.prototype = {
add: function(element) {
this.list.push(element);
},
clear: function() {
this.list = [];
}
};
I've been thinking about how to display the newest array (because the array list would update from time to time.). I think there's a default function to it but I can't find it. Anyone knows it?
var bgImg = new Array();
bgImg[0] = "background.jpg";
bgImg[1] = "background2.jpg";
bgImg[2] = "background3.jpg";
bgImg[3] = "background4.jpg";
If you want the last element of the array,
>>> a = ['background1','background2'];
["background1", "background2"]
>>> b = a[a.length-1]
"background2"
You shouldn't need to manually assign indexes. Just do bgImg.push('background2.jpg'), and it will mutate the array for you. In your case the syntax would be...
var last = bgImg[bgImg.length-1]
If you want the newest then you need to make a variable and set it with whatever you update when you push the newest one, if it doesn't become the last one.
You could create a little object to handle this for you.
function creatImageState() {
var images = [];
return {
get latest() {
return images[images.length - 1];
},
set latest (value) {
images.push(value);
}
};
}
var s = creatImageState();
s.latest = "a.png";
s.latest = "b.png";
alert(s.latest);
IE doesn't support getters and setters so you probably need to use this.
function creatImageState() {
var images = [];
return {
getLatest : function() {
return images[images.length - 1]
},
setLatest : function(value) {
images.push(value);
}
};
}
var s = creatImageState();
s.setLatest("a.png");
s.setLatest("b.png");
alert(s.getLatest());