# File actionview/lib/action_view/helpers/javascript_helper.rb, line 27
def escape_javascript(javascript)
  javascript = javascript.to_s
  if javascript.empty?
    result = ""
  else
    result = javascript.gsub(/(\\|<\/|\r\n|\342\200\250|\342\200\251|[\n\r"'])/u) { |match| JS_ESCAPE_MAP[match] }
  end
  javascript.html_safe? ? result.html_safe : result
end

Escapes carriage returns and single and double quotes for JavaScript segments.

Also available through the alias j(). This is particularly helpful in JavaScript responses, like:

$('some_element').replaceWith('<%= j render 'some/element_template' %>');

# File actionview/lib/action_view/helpers/javascript_helper.rb, line 74
def javascript_tag(content_or_options_with_block = nil, html_options = {}, &block)
  content =
    if block_given?
      html_options = content_or_options_with_block if content_or_options_with_block.is_a?(Hash)
      capture(&block)
    else
      content_or_options_with_block
    end

  if html_options[:nonce] == true
    html_options[:nonce] = content_security_policy_nonce
  end

  content_tag("script", javascript_cdata_section(content), html_options)
end

Returns a JavaScript tag with the content inside. Example:

javascript_tag "alert('All is good')"

Returns:

<script>
//<![CDATA[
alert('All is good')
//]]>
</script>

html_options may be a hash of attributes for the <script> tag.

javascript_tag "alert('All is good')", defer: 'defer'

Returns:

<script defer="defer">
//<![CDATA[
alert('All is good')
//]]>
</script>

Instead of passing the content as an argument, you can also use a block in which case, you pass your html_options as the first parameter.

<%= javascript_tag defer: 'defer' do -%>
  alert('All is good')
<% end -%>

If you have a content security policy enabled then you can add an automatic nonce value by passing nonce: true as part of html_options. Example:

<%= javascript_tag nonce: true do -%>
  alert('All is good')
<% end -%>