ifelseAsync

    If a predicate function returns a truthy value, return x; otherwise, return y.

    Usage

    var ifelseAsync = require( '@stdlib/utils/async/if-else' );
    

    ifelseAsync( predicate, x, y, done )

    If a predicate function returns a truthy value, returns x; otherwise, returns y.

    var randu = require( '@stdlib/random/base/randu' );
    
    function predicate( clbk ) {
        setTimeout( onTimeout, 0 );
        function onTimeout() {
            clbk( null, randu() > 0.5 );
        }
    }
    
    function done( error, result ) {
        if ( error ) {
            throw error;
        }
        console.log( result );
    }
    
    ifelseAsync( predicate, 1.0, -1.0, done );
    

    The predicate function is provided a single argument:

    • clbk: callback to invoke upon predicate function completion

    The callback accepts two arguments:

    • error: error object
    • bool: condition used to determine whether to return x or y

    The done callback is invoked upon function completion and is provided at most two arguments:

    • error: error object
    • result: either x or y

    Notes

    • Execution is not guaranteed to be asynchronous. To guarantee asynchrony, wrap the done callback 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 ifelseAsync = require( '@stdlib/utils/async/if-else' );
    
    var i;
    
    function next() {
        ifelseAsync( predicate, 'BOOP', 'beep', done );
    }
    
    function predicate( clbk ) {
        setTimeout( onTimeout, 0 );
        function onTimeout() {
            clbk( null, randu() > 0.9 );
        }
    }
    
    function done( error, result ) {
        if ( error ) {
            throw error;
        }
        i += 1;
        console.log( result );
        if ( i < 100 ) {
            return next();
        }
    }
    
    i = 0;
    next();