Specify a size for a Shopify image asset url. Equivalent to the liquid image size filter: `{{ image | img_url: "medium" }}`

imgURL.js

String.prototype.imgURL = function(size) {
  // remove any current image size then add the new image size
  return this
    .replace(/_(pico|icon|thumb|small|compact|medium|large|grande|original|1024x1024|2048x2048|master)+\./g, '.')
    .replace(/\.jpg|\.png|\.gif|\.jpeg/g, function(match) {
      return '_'+size+match;
    })
  ;
};

// example 
'//cdn.shopify.com/s/files/1/0087/0462/products/shirt14.jpeg?v=1309278311'.imgURL('medium');
// outputs
'//cdn.shopify.com/s/files/1/0087/0462/products/shirt14_medium.jpeg?v=1309278311'



// alternatively, if you don't want to use a polyfil
function imgURL(src, size) {
  // remove any current image size then add the new image size
  return src
    .replace(/_(pico|icon|thumb|small|compact|medium|large|grande|original|1024x1024|2048x2048|master)+\./g, '.')
    .replace(/\.jpg|\.png|\.gif|\.jpeg/g, function(match) {
      return '_'+size+match;
    })
  ;
}

// example
imgURL('//cdn.shopify.com/s/files/1/0087/0462/products/shirt14.jpeg?v=1309278311', 'medium');
// outputs
'//cdn.shopify.com/s/files/1/0087/0462/products/shirt14_medium.jpeg?v=1309278311'