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

Question

I work on angular 7 I face issue countrows variable give me undefined value

although I assigned it with value as below

Expected result I need is to get value 3 from returned array of object

public Countrows:Number;
ngOnInit(): void {
countitems()
console.log("final count rows is" + this.Countrows);

}
countitems()
{
this._inventory.GetcountItems().subscribe(
data =>this.Countrows=data[0].countItems

)
}
it give me final data undefined

data returned on variable Countrows

[
{
"countItems": 3
}
]

What I have tried:

console.log("final data" + data[0].countItems)
give me on console as
final data 3

Satya Karki · Answer

Hi, Typescript/Javascript functions are of asyncronous behaviour so it does not wait for first function to complete and give undefined from next function. public Countrows:Number; ngOnInit(): void { countitems() // before this function gets complete console.log("final count rows is" + this.Countrows); // this is executing before getting api response. } countitems() { this._inventory.GetcountItems().subscribe( data =>this.Countrows=data[0].countItems console.log('Actual ' + this.Countrows);// this will give correct output ) } 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.

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

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