[Responsive image] Pug/Nunjucks responsive image mixin/macro #responsive

macro.html

{% macro respImg(
  class,
  srcset,
  sizes,
  src,
  width = "", 
  height = "", 
  loading = "",
  alt = ""
)%}
<img 
  class="{{ class }}"
  srcset="{{ srcset }}"
  sizes="{{ sizes }}"   
  src="{{ src }}"
  {% if width %} width="{{ width }}" {% endif %}
  {% if height %}  height="{{ height }}" {% endif %}
  {% if loading %} loading="{{ loading }}" {% endif %}
  alt="{{ alt }}"
/>
{% endmacro %}

{# {{ respImg( 
  class = "__img", 
  srcset = "images/image.png 300w, images/image@2x.png 600w",
  sizes = "(min-width: 1000px) 400px, (min-width: 768px) 300px, 100vw",
  src = "images/image.png",
  loading = "lazy",
  alt = ""
)}}  #}

mixin.pug

mixin respImg(src, initialWidth)
  - const src1 = `${src} ${initialWidth}w`
  - const src2 = `${src.replace(/(\.[\w]+)/, "@1\.5x$1")} ${Math.round(initialWidth * 1.5)}w`
  - const src3 = `${src.replace(/(\.[\w]+)/, "@2x$1")} ${Math.round(initialWidth * 2)}w`

  img(srcset = `${src1}, ${src2}, ${src3}`, src = src)&attributes(attributes)

//- Input
+respImg("images/flower.jpg", 300)(class="block__img" sizes="(min-width: 1000px) 400px, (min-width: 768px) 300px, 100vw" alt="Rose")

//- Output
<img class="block__img" srcset="images/flower.jpg 300w, images/flower@1.5x.jpg 450w, images/flower@2x.jpg 600w" sizes="(min-width: 1000px) 400px, (min-width: 768px) 300px, 100vw" src="images/flower.jpg" alt="Rose"/>