Value of countrows variable give me undefined although I assign it?

Hi,

 

Typescript/Javascript functions are of asyncronous behaviour so it does not wait for first function to complete and give undefined from next function.

1. public Countrows:Number;    
2. ngOnInit(): void {    
3. countitems() // before this function gets complete    
4. console.log("final count rows is" + this.Countrows); // this is executing before getting api response.    
5.     
6. }    
7. countitems()    
8.  {    
9.   this._inventory.GetcountItems().subscribe(    
10.     data =>this.Countrows=data[0].countItems     
11.       console.log('Actual ' + this.Countrows);// this will give correct output    
12.   )    
13.  }    

If you check console output then you will get as:

 

 final count rows is undefined // first

 Actual 3 // second

 

This is because your this funtion console.log("final count rows is" + this.Countrows);  will not wait for this countitems().

 

This is why they are asyncronous.