Get value from anonymous function TypeScript

Question

I have a Angular project and I use the Signalr inside it. But when I get the connectionId , I can print it. But I can't assign it in the global variable. This is my code:

   connection = new signalR.HubConnectionBuilder().withUrl("http://localhost:8178/notifyHub").build();
    connection.start().then(function () {
      connection.invoke("GetConnectionId").then(function (connectionId) {
       console.log(connectionId);
       // var temp=connectionId
      })
    }).catch(err => console.error(err));

declare outside typescript class var temp="" or inside typescript constructor var temp:string = ""; and then assign inside typescript class. — Joel Joseph
– Joel Joseph, Commented Oct 14, 2019 at 5:36
The problem is the scope of your function. As per @jitender's answer, fat arrow notation will allow the use of the correct scope, unless you implicitly want block level scope. — Dane Brouwer
– Dane Brouwer, Commented Oct 14, 2019 at 6:05
@mohammadalmasi accepted ans is not the right way to solve the problem — jitender
– jitender, Commented Oct 14, 2019 at 6:16

Joel Joseph · Accepted Answer · 2019-10-14 06:44:02Z

3

You can solve the same using the following :

temp;   
let self = this;
let connection = new signalR.HubConnectionBuilder().withUrl("http://localhost:8178/notifyHub").build();
connection.start().then(function () {
  connection.invoke("GetConnectionId").then(function (connectionId) {
    console.log(connectionId);
    self.temp = connectionId;
  })
}).catch(err => console.error(err));

or the better solution is to use use arrow function expression :

temp;
connection = new signalR.HubConnectionBuilder().withUrl("http://localhost:8178/notifyHub").build();
connection.start().then(() => {
  connection.invoke("GetConnectionId").then((connectionId) => {
    console.log(connectionId);
    this.temp = connectionId;
  })
}).catch(err => console.error(err)

edited Oct 14, 2019 at 6:44

answered Oct 14, 2019 at 5:56

Joel Joseph

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4 Comments

jitender Over a year ago

any reason behind not using arrow function and performing extra steps to active the same thing?

Joel Joseph Over a year ago

@jitender you are right using arrow functions is better , i have nothing against it though :)

jitender Over a year ago

you can update your answer to use arrow function so later if someone else come here with same problem then OP should goes to right direction

Joel Joseph Over a year ago

@jitender i have updated the answer as you requested

jitender · Accepted Answer · 2019-10-14 05:42:53Z

2

instead of function use arrow function expressions like

connection = new 

   signalR.HubConnectionBuilder().withUrl("http://localhost:8178/notifyHub").build();
    connection.start().then(()=> {
      connection.invoke("GetConnectionId").then((connectionId)=> {
       console.log(connectionId);
       // here you will be able to access this
      })
    }).catch(err => console.error(err));

answered Oct 14, 2019 at 5:42

jitender

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2 Comments

Mohammad Almasi Over a year ago

@jitender Why this way the first value is always undefined??

jitender Over a year ago

first value means?

Imranmadbar · Accepted Answer · 2019-10-14 05:52:37Z

0

Try this way:

connectionId: any;

connection = new 
   signalR.HubConnectionBuilder().withUrl("http://localhost:8178/notifyHub").build();
   connection.start().then(function () {
   connection.invoke("GetConnectionId").then(function (connectionId) {
   console.log(connectionId);

    this.connectionId = connectionId 

  })
}).catch(err => console.error(err));

answered Oct 14, 2019 at 5:52

Imranmadbar

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