var start = 0;
var end = 100;
var duration = 1500;

var startTime = Date.now();
function animate() {
    var delta = Math.min( 1500, Date.now() - startTime );
    var value = ( delta / duration ) * ( end - start ) + start;
    console.log( value );
    if ( delta < 1500 ) {
        requestAnimationFrame( animate );
    }
}
animate();