Develop Reference

Blank screen in vue.js if not using created() life cycle hook or spread operator (...)

The following example gives me a blank screen (jsfiddle here). Even the parts which have nothing to do with the loop are not being rendered.
HTML:
<div id="app">
<button #click="objectFromApi">
run objectFromApi function
</button>
<div
v-for="obj in myObject[0].results"
:key="obj.id"
>
<p>
{{ obj.message }}
</p>
</div>
</div>
JavaScript:
new Vue({
el: "#app",
data: {
myObject: []
},
methods: {
objectFromApi: function(){
this.myObject.push(
{
"count": 5,
"results": [
{
"id": 1,
"message": "object 1"
},
{
"id": 2,
"message": "object 2"
}
]
}
)
}
},
//created() {
// this.objectFromApi()
//}
})
Nevertheless it does work if:
1.) Either using objectFromApi function directly in the created life cycle hook (what I don't want!)
created() {
this.objectFromApi()
}
2.) Or (without the use of created life cycle hook) if I go directly into the nested results array and spread the objects out like this (what I also don't want!)
this.myObject.push(
...{
"count": 5,
"next": "http://127.0.0.1:8000/api/someurl/?page=2",
"previous": null,
"results": [
{
"id": 1,
"message": "object 1"
},
{
"id": 2,
"message": "object 2"
}
]
}.results
)
When using option 2.) of course the v-for loop has to look different:
v-for="obj in myObject" instead of v-for="obj in myObject[0].results"
What is wrong with my initial example?

When the component is first rendering the array myObject will be empty.
During rendering it attempts this:
<div
v-for="obj in myObject[0].results"
:key="obj.id"
>
The value of myObject[0] will be undefined. Attempting to access the results property of undefined will result in an error. This error will cause rendering to fail. Nothing will be shown, even the parts that didn't fail.
There are various ways to fix this problem. You could prepopulate the data with suitable empty properties:
data: {
myObject: [
{
results: []
}
]
}
Alternatively, as you've noted, you could change the loop to use v-for="obj in myObject", changing objectFromApi accordingly to only store the results array in myObject. Even if you don't want that exact change some similar change is probably a good idea because the [0] part strongly suggests you've got a problem with your data model. The key thing here is that it avoids trying to access nested objects that don't exist. The use of the spread operator in your second example is largely irrelevant.
Or you could skip the loop in the template:
<template v-if="myObject[0]">
<div
v-for="obj in myObject[0].results"
:key="obj.id"
>
...
</div>
</template>

angular 5: setting (click) value from an object not working

I have a nav menu that is rendered using a navigation.ts json file for the menu items. When it gets to the navitem component it uses a ngIf to check if the item from the navigation file has a "function" key and if it does, the desired behavior is for it to use the string value from item.function in the object to fill the value for the (click) event.
In reality, the console throws an error saying "_co.item.function is not a function"
HTML
<span class="nav-link" *ngIf="item.function" (click)="item.function()" matRipple>
<mat-icon class="nav-link-icon" *ngIf="item.icon">{{item.icon}}</mat-icon>
<span class="nav-link-title" [translate]="item.translate">{{item.title}}</span>
<span class="nav-link-badge" *ngIf="item.badge" [translate]="item.badge.translate"
[ngStyle]="{'background-color': item.badge.bg,'color': item.badge.fg}">
{{item.badge.title}}
</span>
</span>
Navigation.ts
[{
"id": "accounting",
"title": "Accounting",
"type": "collapse",
"children": [
{
"id" : "salesmenSalesLocation",
"title": "Salesmen Sales Location",
"type": "item",
"function": "handleSelect(ReportTypes.SalesmenSalesLocations)"
},
{
"id": "laggingLedgerEntries",
"title": "Lagging Ledger Entries",
"type": "item",
"function": "handleSelect(ReportTypes.LaggingLedgerEntries)"
}
]}]
I have also tried it as (click)="item.function" with no success.

I'm assuming you can change the data source here, because otherwise I don't see any good solution.
A string is not a function, and while you can turn it into one with eval that is a bad idea. What you should really do instead is just pass in a value that tells the function what to use.
Change your data to something like this:
{
"id" : "salesmenSalesLocation",
"title": "Salesmen Sales Location",
"type": "item",
"reportTypeSource": "SalesmenSalesLocations"
},
{
"id": "laggingLedgerEntries",
"title": "Lagging Ledger Entries",
"type": "item",
"reportTypeSource": "LaggingLedgerEntries"
}
Then pass that value to your function and use that to tell it where to look:
handleSelect (reportTypeSource: string) {
const reportType = ReportTypes[reportTypeSource]
// continue as before
}
And call it in your HTML like this:
(click)="handleSelect(item.reportTypeSource)"

Problem lies here:
"function": "handleSelect(ReportTypes.LaggingLedgerEntries)"
And here:
(click)="item.function()"
You cannot simply pass a string and expect the component to execute a function and also know exactly what to do. Here you need to pass the actual function.
Your setup looks over-config'd. I would tear the config down and put the logic into the component itself. Don't be afraid to have more template as well, if anything it makes things more legible (as opposed to the config)

Does that function exist in the component or just the model? If it is just on the model it won't work. (click) is looking for a method on the component. It is, ostensibly just a string in this instance.

how to fetch json data in scope variable angularjs

Here is my Json data
"data": {
"address": {
"postalCode": "112629",
"state": "DL",
"city": "new city",
"streetAddress": "my street"
},
"specialities": [
{
"_id": "577692f7",
"name": "Football",
"description": "game",
"__v": 0
}
]
}
$scope.test = data;
i am fetching data in html by
ng-repeat="mytest in test" than
mytest.address.city // this is working fine
mytest.specialities.name // not printing anything
i am facing the problem in accessing the specialities name i think that is because of specialities is a array but don't know how to get it.

You defined a specialities object with only one array inside
try
mytest.specialities[0].name
Update:
Also you may want to make sure that the array has at least one element, otherwise you mayget a TypeError: Cannot read property 'name' of undefined.
So the code sould look like this:
mytest.specialities.length > 0 ? mytest.specialities[0].name : '(some default value)';

Assuming there will be many specialities you should use ng-repeat to display them all.
<p ng-repeat="s in mytest.specialities"> {{s.name}} / {{s._id}} / {{s.description}} </p>

Yes mytest.specialities is array. JSON has two possible options [ ] - array, { } - object. In this situation we have array of objects - [ { /* object data */ } ] so to get object parameter first go to array element like this ( example getting first element on index 0 ):
mytest.specialities[0].name
second element:
mytest.specialities[1].name
example each:
<div ng-repeat="special in mytest.specialities">
<span>{{special.name}}</span>
</div>
of course before that set mytest to scope like:
$scope.mytest=mytest;//mytest is your data structure

Angular select and ng-options

I have this angular select:
<select ng-model='obj.status' ng-options='status.code as (status.code + " " + status.phrase) for status in status_codes.data track by status.code'>`
My $scope.status_codes is like this:
data: [
{
"code":"100",
"phrase":"...",
"spec_title":"RFC7231#6.2",
"spec_href":"http://tools.ietf.org/html/rfc7231#section-6.2"
}
...
]
My $scope.obj.status is updated to "300" or "100" or whatever as I change my select, but the select display is always blank. So, the model updates to the selected value of the select input but the input does not show the currently selected value, it shows a blank item.
If i change ng-options to be ng-options='status as (status.code ...' it works, but I only want status.code in my model, not the whole status array. What gives?
I have {{obj | json }} in my HTML and it reads:
obj = {
"name": "",
"description": "",
"payload": "",
"status": "200",
"responseHeaders": {
"entry": [
{
"key": "",
"value": ""
},
{
"key": "",
"value": ""
}
]
}
}

Remove track by.
From the Docs:
Be careful when using select as and track by in the same expression.
My best guess is that the as uses a normal value, like "300", but the track by is using a typed value, like "int:300". Removing one or the other should do it, preferably the track by.
They are giving this as an example:
This will work:
<select ng-options="item as item.label for item in items track by item.id" ng-model="selected"></select>
but this will not work:
<select ng-options="item.subItem as item.label for item in items track by item.id" ng-model="selected"></select>

According to the docs here: https://docs.angularjs.org/api/ng/directive/ngOptions:
select as label for value in array
So in your example this should work (you will get code value as select value in model):
status.code as (status.code + " " + status.phrase) for status in status_codes.data
track by should be used when you have object as value in model, array of objects for options and you want to match current model value to one of objects in array.

Display an Array inside Object using ng-repeat -AngularJs

Below is my JSON object which I would like to display the name in both the parent and child array.
$scope.result= [
{
"id": 1,
"name": "1002",
"parentArray": [
{
"id": 28,
"name": "PRODP1",
"shortCode": "PRODP1"
}
]
}
I want to display Name:1002 Parent_Name:PRODP1
I tried {{item.name}} which will only display 1002.But I need to display the name of parentArray as well.

Since the parentArray is also an array your going to need a nested ng-repeat.
If this is a large page then this may cause a performance issue.
<div ng-repeat="item in result">
{{item.name}}
<div ng-repeat="innerItem in item.parentArray">
{{innerItem.name}}
</div>
</div>

parentArray is an...array, so you need to access it using an index:
<div ng-repeat="item in result">
Name: {{ item.name }} Parent_Name: {{ item.parentArray.length ? item.parentArray[0].name : '' }}
</div>
That's under the assumption that there is one object in parentArray. You might need to iterate it, or you might need to check to see if it exists depending on your requirements.