Converts a callback API to a function that returns an Observable.

bindCallback<T>(callbackFunc: Function, resultSelector?: Function | SchedulerLike, scheduler?: SchedulerLike): (...args: any[]) => Observable<T>

Parameters

callbackFunc	Type: Function.
resultSelector	Optional. Default is undefined. Type: Function | SchedulerLike.
scheduler	Optional. Default is undefined. The scheduler on which to schedule the callbacks.

Returns

(...args: any[]) => Observable<T>: A function which returns the Observable that delivers the same values the callback would deliver.

Description

Give it a function f of type f(x, callback) and it will return a function g that when called as g(x) will output an Observable.

bindCallback is not an operator because its input and output are not Observables. The input is a function func with some parameters. The last parameter must be a callback function that func calls when it is done.

The output of bindCallback is a function that takes the same parameters as func, except the last one (the callback). When the output function is called with arguments it will return an Observable. If function func calls its callback with one argument, the Observable will emit that value. If on the other hand the callback is called with multiple values the resulting Observable will emit an array with said values as arguments.

It is very important to remember that input function func is not called when the output function is, but rather when the Observable returned by the output function is subscribed. This means if func makes an AJAX request, that request will be made every time someone subscribes to the resulting Observable, but not before.

The last optional parameter - scheduler - can be used to control when the call to func happens after someone subscribes to Observable, as well as when results passed to callback will be emitted. By default, the subscription to an Observable calls func synchronously, but using async as the last parameter will defer the call to func, just like wrapping the call in setTimeout with a timeout of 0 would. If you were to use the async Scheduler and call subscribe on the output Observable, all function calls that are currently executing will end before func is invoked.

By default, results passed to the callback are emitted immediately after func invokes the callback. In particular, if the callback is called synchronously, then the subscription of the resulting Observable will call the next function synchronously as well. If you want to defer that call, you may use async just as before. This means that by using Scheduler.async you can ensure that func always calls its callback asynchronously, thus avoiding terrifying Zalgo.

Note that the Observable created by the output function will always emit a single value and then complete immediately. If func calls the callback multiple times, values from subsequent calls will not appear in the stream. If you need to listen for multiple calls, you probably want to use fromEvent or fromEventPattern instead.

If func depends on some context (this property) and is not already bound, the context of func will be the context that the output function has at call time. In particular, if func is called as a method of some objec and if func is not already bound, in order to preserve the context it is recommended that the context of the output function is set to that object as well.

If the input function calls its callback in the "node style" (i.e. first argument to callback is optional error parameter signaling whether the call failed or not), bindNodeCallback provides convenient error handling and probably is a better choice. bindCallback will treat such functions the same as any other and error parameters (whether passed or not) will always be interpreted as regular callback argument.

Examples

Convert jQuery's getJSON to an Observable API

import { bindCallback } from 'rxjs';
import * as jQuery from 'jquery';

// Suppose we have jQuery.getJSON('/my/url', callback)
const getJSONAsObservable = bindCallback(jQuery.getJSON);
const result = getJSONAsObservable('/my/url');
result.subscribe(x => console.log(x), e => console.error(e));

Receive an array of arguments passed to a callback

import { bindCallback } from 'rxjs';

const someFunction = (a, b, c) => {
  console.log(a); // 5
  console.log(b); // 'some string'
  console.log(c); // {someProperty: 'someValue'}
};

const boundSomeFunction = bindCallback(someFunction);
boundSomeFunction().subscribe(values => {
  console.log(values) // [5, 'some string', {someProperty: 'someValue'}]
});

Compare behaviour with and without async Scheduler

import { bindCallback } from 'rxjs';

function iCallMyCallbackSynchronously(cb) {
  cb();
}

const boundSyncFn = bindCallback(iCallMyCallbackSynchronously);
const boundAsyncFn = bindCallback(iCallMyCallbackSynchronously, null, Rx.Scheduler.async);

boundSyncFn().subscribe(() => console.log('I was sync!'));
boundAsyncFn().subscribe(() => console.log('I was async!'));
console.log('This happened...');

// Logs:
// I was sync!
// This happened...
// I was async!

Use bindCallback on an object method

import { bindCallback } from 'rxjs';

const boundMethod = bindCallback(someObject.methodWithCallback);
boundMethod.call(someObject) // make sure methodWithCallback has access to someObject
.subscribe(subscriber);

Overloads

bindCallback(callbackFunc: Function, resultSelector: Function, scheduler?: SchedulerLike): (...args: any[]) => Observable<any>

Parameters

callbackFunc	Type: Function.
resultSelector	Type: Function.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(...args: any[]) => Observable<any>

bindCallback(callbackFunc: (callback: (res1: R1, res2: R2, res3: R3, res4: R4, ...args: any[]) => any) => any, scheduler?: SchedulerLike): () => Observable<any[]>

Parameters

callbackFunc	Type: (callback: (res1: R1, res2: R2, res3: R3, res4: R4, ...args: any[]) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

() => Observable<any[]>

bindCallback(callbackFunc: (callback: (res1: R1, res2: R2, res3: R3) => any) => any, scheduler?: SchedulerLike): () => Observable<[R1, R2, R3]>

Parameters

callbackFunc	Type: (callback: (res1: R1, res2: R2, res3: R3) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

() => Observable<[R1, R2, R3]>

bindCallback(callbackFunc: (callback: (res1: R1, res2: R2) => any) => any, scheduler?: SchedulerLike): () => Observable<[R1, R2]>

Parameters

callbackFunc	Type: (callback: (res1: R1, res2: R2) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

() => Observable<[R1, R2]>

bindCallback(callbackFunc: (callback: (res1: R1) => any) => any, scheduler?: SchedulerLike): () => Observable<R1>

Parameters

callbackFunc	Type: (callback: (res1: R1) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

() => Observable<R1>

bindCallback(callbackFunc: (callback: () => any) => any, scheduler?: SchedulerLike): () => Observable<void>

Parameters

callbackFunc	Type: (callback: () => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

() => Observable<void>

bindCallback(callbackFunc: (arg1: A1, callback: (res1: R1, res2: R2, res3: R3, res4: R4, ...args: any[]) => any) => any, scheduler?: SchedulerLike): (arg1: A1) => Observable<any[]>

Parameters

callbackFunc	Type: (arg1: A1, callback: (res1: R1, res2: R2, res3: R3, res4: R4, ...args: any[]) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1) => Observable<any[]>

bindCallback(callbackFunc: (arg1: A1, callback: (res1: R1, res2: R2, res3: R3) => any) => any, scheduler?: SchedulerLike): (arg1: A1) => Observable<[R1, R2, R3]>

Parameters

callbackFunc	Type: (arg1: A1, callback: (res1: R1, res2: R2, res3: R3) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1) => Observable<[R1, R2, R3]>

bindCallback(callbackFunc: (arg1: A1, callback: (res1: R1, res2: R2) => any) => any, scheduler?: SchedulerLike): (arg1: A1) => Observable<[R1, R2]>

Parameters

callbackFunc	Type: (arg1: A1, callback: (res1: R1, res2: R2) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1) => Observable<[R1, R2]>

bindCallback(callbackFunc: (arg1: A1, callback: (res1: R1) => any) => any, scheduler?: SchedulerLike): (arg1: A1) => Observable<R1>

Parameters

callbackFunc	Type: (arg1: A1, callback: (res1: R1) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1) => Observable<R1>

bindCallback(callbackFunc: (arg1: A1, callback: () => any) => any, scheduler?: SchedulerLike): (arg1: A1) => Observable<void>

Parameters

callbackFunc	Type: (arg1: A1, callback: () => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1) => Observable<void>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, callback: (res1: R1, res2: R2, res3: R3, res4: R4, ...args: any[]) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2) => Observable<any[]>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, callback: (res1: R1, res2: R2, res3: R3, res4: R4, ...args: any[]) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2) => Observable<any[]>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, callback: (res1: R1, res2: R2, res3: R3) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2) => Observable<[R1, R2, R3]>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, callback: (res1: R1, res2: R2, res3: R3) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2) => Observable<[R1, R2, R3]>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, callback: (res1: R1, res2: R2) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2) => Observable<[R1, R2]>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, callback: (res1: R1, res2: R2) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2) => Observable<[R1, R2]>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, callback: (res1: R1) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2) => Observable<R1>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, callback: (res1: R1) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2) => Observable<R1>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, callback: () => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2) => Observable<void>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, callback: () => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2) => Observable<void>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, callback: (res1: R1, res2: R2, res3: R3, res4: R4, ...args: any[]) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3) => Observable<any[]>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, callback: (res1: R1, res2: R2, res3: R3, res4: R4, ...args: any[]) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3) => Observable<any[]>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, callback: (res1: R1, res2: R2, res3: R3) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3) => Observable<[R1, R2, R3]>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, callback: (res1: R1, res2: R2, res3: R3) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3) => Observable<[R1, R2, R3]>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, callback: (res1: R1, res2: R2) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3) => Observable<[R1, R2]>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, callback: (res1: R1, res2: R2) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3) => Observable<[R1, R2]>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, callback: (res1: R1) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3) => Observable<R1>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, callback: (res1: R1) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3) => Observable<R1>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, callback: () => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3) => Observable<void>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, callback: () => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3) => Observable<void>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, callback: (res1: R1, res2: R2, res3: R3, res4: R4, ...args: any[]) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3, arg4: A4) => Observable<any[]>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, callback: (res1: R1, res2: R2, res3: R3, res4: R4, ...args: any[]) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3, arg4: A4) => Observable<any[]>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, callback: (res1: R1, res2: R2, res3: R3) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3, arg4: A4) => Observable<[R1, R2, R3]>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, callback: (res1: R1, res2: R2, res3: R3) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3, arg4: A4) => Observable<[R1, R2, R3]>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, callback: (res1: R1, res2: R2) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3, arg4: A4) => Observable<[R1, R2]>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, callback: (res1: R1, res2: R2) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3, arg4: A4) => Observable<[R1, R2]>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, callback: (res1: R1) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3, arg4: A4) => Observable<R1>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, callback: (res1: R1) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3, arg4: A4) => Observable<R1>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, callback: () => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3, arg4: A4) => Observable<void>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, callback: () => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3, arg4: A4) => Observable<void>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5, callback: (res1: R1, res2: R2, res3: R3, res4: R4, ...args: any[]) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5) => Observable<any[]>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5, callback: (res1: R1, res2: R2, res3: R3, res4: R4, ...args: any[]) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5) => Observable<any[]>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5, callback: (res1: R1, res2: R2, res3: R3) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5) => Observable<[R1, R2, R3]>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5, callback: (res1: R1, res2: R2, res3: R3) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5) => Observable<[R1, R2, R3]>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5, callback: (res1: R1, res2: R2) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5) => Observable<[R1, R2]>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5, callback: (res1: R1, res2: R2) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5) => Observable<[R1, R2]>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5, callback: (res1: R1) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5) => Observable<R1>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5, callback: (res1: R1) => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5) => Observable<R1>

bindCallback(callbackFunc: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5, callback: () => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5) => Observable<void>

Parameters

callbackFunc	Type: (arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5, callback: () => any) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(arg1: A1, arg2: A2, arg3: A3, arg4: A4, arg5: A5) => Observable<void>

bindCallback(callbackFunc: (...args: Array<A | ((result: R) => any)>) => any, scheduler?: SchedulerLike): (...args: A[]) => Observable<R>

Parameters

callbackFunc	Type: (...args: Array any)>) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(...args: A[]) => Observable<R>

bindCallback(callbackFunc: (...args: Array<A | ((...results: R[]) => any)>) => any, scheduler?: SchedulerLike): (...args: A[]) => Observable<R[]>

Parameters

callbackFunc	Type: (...args: Array any)>) => any.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(...args: A[]) => Observable<R[]>

bindCallback(callbackFunc: Function, scheduler?: SchedulerLike): (...args: any[]) => Observable<any>

Parameters

callbackFunc	Type: Function.
scheduler	Optional. Default is undefined. Type: SchedulerLike.

Returns

(...args: any[]) => Observable<any>

See Also

• bindNodeCallback
• from