在 Javascript 中为 gulpfile.js 舍入 const 变量列表的更好方法？

Question

在我的 gulpfile.js 中，我希望能够根据使用 gulp 插件“gulp-sharp-responsive”的图像大小/压缩任务占用的屏幕的大致百分比来计算宽度。

例如，我的全屏图像尺寸之一是 1200。对于 1/4 宽度的图像，我希望它输出 300 像素的图像吗？ 我想避免手动计算新宽度并能够将除数设置为命令行选项，所以这是我在本教程https://www.sitepoint 之后提出的以下方法的解决方案。 com/pass-parameters-gulp-tasks/ 。

在 gulpfile.js 的顶部，我添加了以下代码：

// fetch command line arguments
const arg = (argList => {
    let arg = {}, a, opt, thisOpt, curOpt;
    for (a = 0; a < argList.length; a++) {
        thisOpt = argList[a].trim();
        opt = thisOpt.replace(/^\-+/, '');
        if (opt === thisOpt) {
            // argument value
            if (curOpt) arg[curOpt] = opt;
            curOpt = null;
        }
        else {

            // argument name
            curOpt = opt;
            arg[curOpt] = true;
        }
    }
    return arg;
})(process.argv);

我将 div 分配为 arg.d 并在 arg 为空时提供了一个回退到 1（即 div = arg.d || 1）。 请注意，由于我主要是要全屏显示宽度为 576 像素及以下（移动屏幕）的特色图像，因此我不会将 xs 大小除以除数。 此外，由于 gulp-sharp-responsive 无法处理非整数宽度，我不得不用 round 函数对商进行四舍五入。 我的问题是，如何让我的代码减少冗余——例如，我不会为每个 const 变量重复 math.round() 。 如果您有任何建议让我的代码更简洁，请告诉我，我只是一个初学者。 谢谢！

function sharpImg() {
    const div = arg.d || 1, xs = (Math.round(576 / div)), sm = (Math.round(769 / div)), md = (Math.round(992 / div)), lg = (Math.round(1200 / div)), xl = (Math.round(1400 / div)), xxl = (Math.round(2048 / div));
    return src(['_images/original/process/**/*.{jpeg,jpg,png,tiff,webp}', '!_images/original/raw/**'])
        .pipe($.rename(function (path) {
            path.dirname += "/" + path.basename;
        }))
        .pipe($.sharpResponsive({
            formats: [
                // jpeg
                { width: xs, format: "jpeg", rename: { suffix: "-xs" }, jpegOptions: { quality: 50, progressive: true } },
                { width: sm, format: "jpeg", rename: { suffix: "-sm" }, jpegOptions: { quality: 50, progressive: true } },
                { width: md, format: "jpeg", rename: { suffix: "-md" }, jpegOptions: { quality: 50, progressive: true } },
                { width: lg, format: "jpeg", rename: { suffix: "-lg" }, jpegOptions: { quality: 50, progressive: true } },
                { width: xl, format: "jpeg", rename: { suffix: "-xl" }, jpegOptions: { quality: 50, progressive: true } },
                { width: xxl, format: "jpeg", rename: { suffix: "-xxl" }, jpegOptions: { quality: 50, progressive: true } },
                // webp
                { width: xs, format: "webp", rename: { suffix: "-xs" }, webpOptions: { quality: 50 } },
                { width: sm, format: "webp", rename: { suffix: "-sm" }, webpOptions: { quality: 50 } },
                { width: md, format: "webp", rename: { suffix: "-md" }, webpOptions: { quality: 50 } },
                { width: lg, format: "webp", rename: { suffix: "-lg" }, webpOptions: { quality: 50 } },
                { width: xl, format: "webp", rename: { suffix: "-xl" }, webpOptions: { quality: 50 } },
                { width: xxl, format: "webp", rename: { suffix: "-xxl" }, webpOptions: { quality: 50 } },
                // avif
                { width: xs, format: "avif", rename: { suffix: "-xs" }, avifOptions: { quality: 50 } },
                { width: sm, format: "avif", rename: { suffix: "-sm" }, avifOptions: { quality: 50 } },
                { width: md, format: "avif", rename: { suffix: "-md" }, avifOptions: { quality: 50 } },
                { width: lg, format: "avif", rename: { suffix: "-lg" }, avifOptions: { quality: 50 } },
                { width: xl, format: "avif", rename: { suffix: "-xl" }, avifOptions: { quality: 50 } },
                { width: xxl, format: "avif", rename: { suffix: "-xxl" }, avifOptions: { quality: 50 } },
            ]
        }))
        .pipe(dest('_images/processed'))
}

导出任务：

exports.sharpImg = sharpImg;

结果：运行“gulp sharpImg”会导致定义默认的 const 宽度，而运行“gulp sharpImg --d 4”会导致图像为其默认宽度的 1/4。

Answer 1

您可以创建一个断点对象，一个执行除法重复 math.floor 的函数，然后使用一些现代 JS majicks，我认为您的代码可以更短，更少重复，但同样可读，重要的是，简单例如更改断点

function sharpImg() {
    const BREAKPOINTS = {
        xs: 576,
        sm: 769,
        md: 992,
        lg: 1200,
        xl: 1400,
        xxl: 2048,
    };
    const onDiv = div => Object.entries(BREAKPOINTS).map(([bp, value]) => [Math.round(value / div), `-${bp}`]);
    // creates an array of [[1, "-xs"], [2, "-sm"], ... ] (obviously the values are 576/div etc)
    
    const div = arg.d || 1, bps = onDiv(div);
    
    const jpegOptions = { quality: 50, progressive: true };
    const webpOptions = { quality: 50 };
    const avifOptions = { quality: 50 };
    
    return src(['_images/original/process/**/*.{jpeg,jpg,png,tiff,webp}', '!_images/original/raw/**'])
        .pipe($.rename(function (path) {
            path.dirname += "/" + path.basename;
        }))
        .pipe($.sharpResponsive({
            formats: [
                // jpeg
                ...bps.map(([width, suffix]) => ({ width, format: "jpeg", rename: { suffix }, jpegOptions })),
                // webp
                ...bps.map(([width, suffix]) => ({ width, format: "webp", rename: { suffix }, webpOptions })),
                // avif
                ...bps.map(([width, suffix]) => ({ width, format: "avif", rename: { suffix }, avifOptions })),
            ]
        }))
        .pipe(dest('_images/processed'))
}

输出format以检查其是否正确的片段

 function sharpImg() { const BREAKPOINTS = { xs: 576, sm: 769, md: 992, lg: 1200, xl: 1400, xxl: 2048, }; const onDiv = div => Object.entries(BREAKPOINTS).map(([bp, value]) => [Math.round(value / div), `-${bp}`]); // creates an array of [[1, "-xs"], [2, "-sm"], ... ] (obviously the values are 576/div etc) const div = 1, bps = onDiv(div); const jpegOptions = { quality: 50, progressive: true }; const webpOptions = { quality: 50 }; const avifOptions = { quality: 50 }; const formats = [ // jpeg ...bps.map(([width, suffix]) => ({ width, format: "jpeg", rename: { suffix }, jpegOptions })), // webp ...bps.map(([width, suffix]) => ({ width, format: "webp", rename: { suffix }, webpOptions })), // avif ...bps.map(([width, suffix]) => ({ width, format: "avif", rename: { suffix }, avifOptions })), ]; return formats; } console.log(JSON.stringify(sharpImg(), null, 4));