Simple function to determine whether a viewport is vertical, horizontal or square, and whether the dimensions are nearest to 16:9, 4:3, or 1:1 (or the vertical equivalent)

anaylzeViewport.js

function analyzeViewport() {
    const width = window.innerWidth;
    const height = window.innerHeight;

    // Determine layout
    let layout;
    if (width > height) {
        layout = "horizontal";
    } else if (width < height) {
        layout = "vertical";
    } else {
        layout = "square";
    }

    // Determine aspect ratio closeness
    const aspectRatio = width / height;
    const ratios = {
        "16:9": 16 / 9,
        "9:16": 9 / 16,
        "4:3": 4 / 3,
        "3:4": 3 / 4,
        "1:1": 1
    };

    let closestRatio = "";
    let smallestDifference = Infinity;

    for (const [ratio, value] of Object.entries(ratios)) {
        const difference = Math.abs(aspectRatio - value);
        if (difference < smallestDifference) {
            smallestDifference = difference;
            closestRatio = ratio;
        }
    }

    return {
        width: width,
        height: height,
        layout: layout,
        closestRatio: closestRatio
    };
}