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- # browser.coffee

- ¶

  This Browser compatibility layer extends core CoffeeScript functions to make things work smoothly when compiling code directly in the browser. We add support for loading remote Coffee scripts via XHR, and `text/coffeescript` script tags, source maps via data-URLs, and so on.

      CoffeeScript = require './coffee-script'
      CoffeeScript.require = require
      compile = CoffeeScript.compile

- ¶

  Use standard JavaScript `eval` to eval code.

      CoffeeScript.eval = (code, options = {}) ->
        options.bare ?= on
        eval compile code, options

- ¶

  Running code does not provide access to this scope.

      CoffeeScript.run = (code, options = {}) ->
        options.bare = on
        options.shiftLine = on
        Function(compile code, options)()

- ¶

  If we’re not in a browser environment, we’re finished with the public API.

      return unless window?

- ¶

  Include source maps where possible. If we’ve got a base64 encoder, a JSON serializer, and tools for escaping unicode characters, we’re good to go. Ported from https://developer.mozilla.org/en-US/docs/DOM/window.btoa

      if btoa? and JSON? and unescape? and encodeURIComponent?
        compile = (code, options = {}) ->
          options.sourceMap = true
          options.inline = true
          {js, v3SourceMap} = CoffeeScript.compile code, options
          "#{js}\n//# sourceMappingURL=data:application/json;base64,#{btoa unescape encodeURIComponent v3SourceMap}\n//# sourceURL=coffeescript"

- ¶

  Load a remote script from the current domain via XHR.

      CoffeeScript.load = (url, callback, options = {}, hold = false) ->
        options.sourceFiles = [url]
        xhr = if window.ActiveXObject
          new window.ActiveXObject('Microsoft.XMLHTTP')
        else
          new window.XMLHttpRequest()
        xhr.open 'GET', url, true
        xhr.overrideMimeType 'text/plain' if 'overrideMimeType' of xhr
        xhr.onreadystatechange = ->
          if xhr.readyState is 4
            if xhr.status in [0, 200]
              param = [xhr.responseText, options]
              CoffeeScript.run param... unless hold
            else
              throw new Error "Could not load #{url}"
            callback param if callback
        xhr.send null

- ¶

  Activate CoffeeScript in the browser by having it compile and evaluate all script tags with a content-type of `text/coffeescript`. This happens on page load.

      runScripts = ->
        scripts = window.document.getElementsByTagName 'script'
        coffeetypes = ['text/coffeescript', 'text/literate-coffeescript']
        coffees = (s for s in scripts when s.type in coffeetypes)
        index = 0

        execute = ->
          param = coffees[index]
          if param instanceof Array
            CoffeeScript.run param...
            index++
            execute()

        for script, i in coffees
          do (script, i) ->
            options = literate: script.type is coffeetypes[1]
            source = script.src or script.getAttribute('data-src')
            if source
              CoffeeScript.load source,
                (param) ->
                  coffees[i] = param
                  execute()
                options
                true
            else
              options.sourceFiles = ['embedded']
              coffees[i] = [script.innerHTML, options]

        execute()

- ¶

  Listen for window load, both in decent browsers and in IE.

      if window.addEventListener
        window.addEventListener 'DOMContentLoaded', runScripts, no
      else
        window.attachEvent 'onload', runScripts