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();

See Also

• @stdlib/utils/async/if-then: if a predicate function returns a truthy value, invoke x; otherwise, invoke y.
• @stdlib/utils/if-else: if a condition is truthy, return x; otherwise, return y.