Small tweening function for the quick tween.

tween.js

export function tween( time, update ) {
    const start = Date.now();

    var isCanceled = false;
    var isComplete = false;

    var chain = [];

    function loop() {
        if ( isCanceled ) return;

        const difference = Date.now() - start;
        const delta = difference / time;

        if ( delta >= 1 ) {
            isComplete = true;
            update( 1 );
            chain.forEach( callback => callback() );
        } else {
            update( delta );
            requestAnimationFrame( loop );
        }
    }

    requestAnimationFrame( loop );

    return {
        cancel() {
            isCanceled = true;
        },

        after( callback ) {
            isComplete ? callback() : chain.push( callback );
        },

        isComplete() {
            return isComplete;
        }
    };
}

This isn't amazingly optimized at all. But it get's the job done in many many use cases I encounter a lot. Obviously no replacement for things like Greensock's GSAP and others.

But these 40 lines (many of which are white space) allow you to:

tween( 1700, t => foo.setFace( t ) ).after( () => some.shenanigans() );