preloading method

preload.coffee

preload = (urls) ->
  for url in urls
    braces = url.match(/{\d\.\.\d}/g)
    if braces
      nums = braces[0].match(/\d/g)
      expanded = []
      for num in [nums[0]..nums[1]]
        expanded.push url.replace(braces[0], num)
      preload expanded
    else
      img = new Image()
      img.onload = ->
        console.log("Preloaded #{this.src}")
      img.src = url
    true


# Usage:

preload ['/static/tilda/loader.png', '/static/tilda/logo_{1..4}.png']

# Log:

# Preloaded http://localhost:8000/static/tilda/logo_1.png
# Preloaded http://localhost:8000/static/tilda/logo_2.png
# Preloaded http://localhost:8000/static/tilda/logo_3.png
# Preloaded http://localhost:8000/static/tilda/logo_4.png
# Preloaded http://localhost:8000/static/tilda/loader.png