Error: The method of promise.then is not recognized as a function

Question

Error: The method of promise.then is not recognized as a function

Having an issue with Rxjs v5 while attempting to run http.get requests one after the other in sequential order. The error message received is

TypeError: promise.then is not a function

. Below is the code snippet in question:

    var http = require('http');
    Rx.Observable
        .from(data)
        .pairwise()
        .concatMap(a => {
            var url = 'http://to/some/api?origins=' + a[0].lat + ',' + a[0].lng + '&destinations=' + a[1].lat + ',' + a[1].lng;
            return Rx.Observable.fromPromise(http.get(url));        
        })    
        .subscribe(item => {
            console.log(item);
        });

javascript node.js rxjs5

Answer 1

Answer №1

The `http.get` method in Node.js does not return a promise, as explained here

Since it uses a non-standard interface, a small custom work-around is needed to make it function properly. Here's a relatively simple implementation:

var http = require('http');
function observableGet(options) {
  return new Rx.Observable(subscriber => {
    var subscription = new Rx.Subscription();

    // Custom logic for making the request and handling data

  });
}

You can then use this custom `observableGet` function instead of `http.get` like this:


Rx.Observable
.from(data)
.pairwise()
.concatMap(a => {
var url = //...url;
return observableGet(url);        
})    
.subscribe(item => {
console.log(item);
});

Alternatively, you could consider using a library that returns Promises, such as request-promise, which may simplify your code.

Answer 2

The `http.get` method in Node.js does not return a promise, as explained here

Since it uses a non-standard interface, a small custom work-around is needed to make it function properly. Here's a relatively simple implementation:

var http = require('http');
function observableGet(options) {
  return new Rx.Observable(subscriber => {
    var subscription = new Rx.Subscription();

    // Custom logic for making the request and handling data

  });
}

You can then use this custom `observableGet` function instead of `http.get` like this:


Rx.Observable
.from(data)
.pairwise()
.concatMap(a => {
var url = //...url;
return observableGet(url);        
})    
.subscribe(item => {
console.log(item);
});

Alternatively, you could consider using a library that returns Promises, such as request-promise, which may simplify your code.

Error: The method of promise.then is not recognized as a function

Answer №1

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