browser.coffee

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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 './coffeescript'
{ compile } = CoffeeScript
```
§

Use window.eval to evaluate code, rather than just eval, to run the script in a clean global scope rather than inheriting the scope of the CoffeeScript compiler. (So that cake test:browser also works in Node, use either window.eval or global.eval as appropriate).
```
CoffeeScript.eval = (code, options = {}) ->
  options.bare ?= on
  globalRoot = if window? then window else global
  globalRoot['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)()

§

Export this more limited CoffeeScript than what is exported by index.coffee, which is intended for a Node environment.
```
module.exports = CoffeeScript
```
§

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?
  compile = (code, options = {}) ->
    options.inlineMap = true
    CoffeeScript.compile code, options
```

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.

CoffeeScript.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
        options.filename = source
        CoffeeScript.load source,
          (param) ->
            coffees[i] = param
            execute()
          options
          true
      else

§

options.filename defines the filename the source map appears as in Developer Tools. If a script tag has an id, use that as the filename; otherwise use coffeescript, or coffeescript1 etc., leaving the first one unnumbered for the common case that there’s only one CoffeeScript script block to parse.
```
        options.filename = if script.id and script.id isnt '' then script.id else "coffeescript#{if i isnt 0 then i else ''}"
        options.sourceFiles = ['embedded']
        coffees[i] = [script.innerHTML, options]

  execute()
```
§

Listen for window load, both in decent browsers and in IE. Only attach this event handler on startup for the non-ES module version of the browser compiler, to preserve backward compatibility while letting the ES module version be importable without side effects.
```
if this is window
  if window.addEventListener
    window.addEventListener 'DOMContentLoaded', CoffeeScript.runScripts, no
  else
    window.attachEvent 'onload', CoffeeScript.runScripts
```