Using Javascript, increase scale of a section from .75 to 1 using window scroll value

Question

I have a very simple function, that waits until a section is "within view" of the viewport. I'm wanting to animate/"grow" the section from something like .75 of it's natural size, to 1.

When I do this, the calculation often stops at say, 0.975 or something, leaving a very small (but very annoying) gap.

Also—it looks a little jittery, and I've tried to use requestAnimationFrame to negate any performance issues, but it still doesn't look great.

const CaseStudyGrow = () => {
    let ticking         = false;
    let case_studies    = document.querySelectorAll('.case_studies');

    if (Object.values(case_studies).length <= 0) {
        return;
    }

    const animate = () => {
        let scroll  = Math.round(window.scrollY);
        let vh      = Math.round(window.innerHeight);

        Object.values(case_studies).forEach(casestudy => {
            let offset = Math.round(casestudy.offsetTop);

            // calc 3/4s of the viewport, to animate the scroll when the section is within a quarter of the viewport from being in view.
            let q       = vh / 4;
            let grace   = q * 3;  
            let target  = parseInt(offset) - parseInt(grace);

            if (((scroll + vh) - offset) > target) {
                let grow    = ((scroll + (vh + vh / 2)) - offset) / 1000;
                grow        = grow.toFixed(5);

                if ((grow >= 0.75) && (grow <= 1)) {
                    casestudy.style.setProperty('--grow', grow);
                }
            } 

            // else {
            //  casestudy.style.setProperty('--grow', '0.75');
            // }
        });
    };

    document.addEventListener('scroll', () => {
        requestAnimationFrame(animate);
    }, false);
};

document.addEventListener('DOMContentLoaded', CaseStudyGrow, false);

Lastly, if you scroll really quickly up and down, the calculation is nowhere near, often stopping around 0.8 or something.

I'm definitely not doing this correctly but I need a solution.

Any help hugely appreciated.

Matt

Tried using Math.ceil / Math.round to get full values.

Tried using requestAnimationFrame to smooth performance.