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ifthenAsync
If a predicate function returns a truthy value, invoke
x; otherwise, invokey.
Installation
npm install @stdlib/utils-async-if-thenUsage
var ifthenAsync = require( '@stdlib/utils-async-if-then' );ifthenAsync( predicate, x, y, done )
If a predicate function returns a truthy value, invokes x; otherwise, invokes y.
var randu = require( '@stdlib/random-base-randu' );
function predicate( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, randu() > 0.5 );
}
}
function x( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, 1.0 );
}
}
function y( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, -1.0 );
}
}
function done( error, result ) {
if ( error ) {
throw error;
}
console.log( result );
}
ifthenAsync( predicate, x, y, done );The predicate function is provided a single argument:
-
clbk: callback to invoke uponpredicatefunction completion
The callback accepts two arguments:
-
error: error object -
bool: condition used to determine whether to invokexory
Both x and y are provided a single argument:
-
clbk: callback to invoke upon function completion
The callback function accepts any number of arguments, with the first argument reserved for providing an error. If the error argument is falsy, the done callback is invoked with its first argument as null and all other provided arguments. If the error argument is truthy, the done callback is invoked with only an error argument.
var randu = require( '@stdlib/random-base-randu' );
function predicate( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, randu() > 0.5 );
}
}
function x( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, 1.0, 2.0, 3.0 );
}
}
function y( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, 4.0, 5.0, 6.0 );
}
}
function done( error, a, b, c ) {
if ( error ) {
throw error;
}
console.log( a, b, c );
}
ifthenAsync( predicate, x, y, done );Notes
- The function is similar to
ifelseAsync(), but allows deferred argument evaluation. - Execution is not guaranteed to be asynchronous. To guarantee asynchrony, wrap the
donecallback in a function which either executes at the end of the current stack (e.g.,nextTick) or during a subsequent turn of the event loop (e.g.,setImmediate,setTimeout).
Examples
var randu = require( '@stdlib/random-base-randu' );
var ceil = require( '@stdlib/math-base-special-ceil' );
var repeatString = require( '@stdlib/string-repeat' );
var ifthenAsync = require( '@stdlib/utils-async-if-then' );
var i;
function next() {
ifthenAsync( predicate, x, y, done );
}
function predicate( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, randu() > 0.9 );
}
}
function x( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, repeatString( 'BOOP', ceil( randu()*3.0 ) ) );
}
}
function y( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, repeatString( 'beep', ceil( randu()*5.0 ) ) );
}
}
function done( error, result ) {
if ( error ) {
throw error;
}
i += 1;
console.log( result );
if ( i < 100 ) {
return next();
}
}
i = 0;
next();See Also
-
@stdlib/utils-async/if-else: if a predicate function returns a truthy value, returnx; otherwise, returny. -
@stdlib/utils-if-then: if a condition is truthy, invokex; otherwise, invokey.
Notice
This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.
Community
License
See LICENSE.
Copyright
Copyright © 2016-2024. The Stdlib Authors.