Greasyfork forum MARKDOWN for new comments

Select MARKDOWN format by default, add help links, add toolbar formatting buttons for markdown
当前为 2014-12-05 提交的版本，查看最新版本。
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// ==UserScript==
// @name          Greasyfork forum MARKDOWN for new comments
// @author        wOxxOm
// @description   Select MARKDOWN format by default, add help links, add toolbar formatting buttons for markdown
// @namespace     wOxxOm.scripts
// @version       1.1
// @include       https://greasyfork.org/*forum/discussion/*
// @include       https://greasyfork.org/*forum/post/discussion*
// @run-at        document-start
// @grant         none
// ==/UserScript==

var ob = new MutationObserver(function(mutations){
  for (var i=0, ml=mutations.length, m; (i<ml) && (m=mutations[i]); i++)
    for (var j=0, nodes=m.addedNodes, nl=nodes.length, n; (j<nl) && (n=nodes[j]); j++)
      if (n.nodeType == 1) {
        if (n.localName == 'label') {
          if (n.for != 'Form_Format2')
            continue;
        } 
        else if (!(n = n.querySelector('label[for="Form_Format2"]')))
          continue;

        n.click();
        addFeatures(n);
        ob.disconnect();
        return;
      }
});
ob.observe(document, {subtree:true, childList:true});

function addFeatures(n) {
  // add formatting help tooltips
  n.previousElementSibling.insertAdjacentHTML('beforeend',
         ' (<a href="/help/allowed-markup" target="_blank" title="'+
         '* (name, title), a (href), abbr, b, blockquote (cite), br, center, cite, code, dd, del, dfn, div, dl, dt, em, '+
         'h1, h2, h3, h4, h5, h6, hr, i, ins, img (alt, height, src (https), width), kbd, li, mark, ol, p, pre, q (cite), '+
         'rp, rt, ruby, s, samp, small, span, strike, strong, tt, table, tbody, tfoot, thead, td, th, tr, sub, sup, '+
         'time (datetime, pubdate), u, ul, var">?</a>)');
  n.insertAdjacentHTML('beforeend',
         ' (<a href="http://www.darkcoding.net/software/markdown-quick-reference/" target="_blank">?</a>)');

  // add buttons
  n.parentNode.textAreaNode = n.parentNode.querySelector('textarea');
  btnMake(n, '<b>B</b>', 'Bold', '**');
  btnMake(n, '<i>I</i>', 'Italic', '*');
  btnMake(n, '<u>U</u>', 'Underline', '<u>','</u>');
  btnMake(n, '<s>S</s>', 'Strikethrough', '<s>','</s>');
  btnMake(n, '---', 'Horizontal line', '\n\n---\n\n', '', true);
  btnMake(n, 'URL', 'Add URL to selected text', 
          function(e) {
            try {edWrapInTag('[', ']('+prompt("URL:")+')', null, e.target)}
            catch(e) {};
          });
  btnMake(n, 'Image (https)', 'Convert selected https://url to inline image', '![image](', ')');
  btnMake(n, 'Table', 'Insert table template', '\n| head1 | head2 |\n|-------|-------|\n| cell1 | cell2 |\n| cell3 | cell4 |\n', '', true);
  btnMake(n, 'Code', 'Apply CODE markdown to selected text',
          function(e){
            var ed = edInit(e.target);
            if (ed.sel.indexOf('\n') < 0)
              edWrapInTag('`', '`', ed);
            else
              edWrapInTag(((ed.sel1==0) || (ed.text.charAt(ed.sel1-1) == '\n') ? '' : '\n') + '```' + (ed.sel.charAt(0) == '\n' ? '' : '\n'),
                          (ed.sel.substr(-1) == '\n' ? '' : '\n') + '```' + (ed.text.substr(ed.sel2,1) == '\n' ? '' : '\n'),
                          ed);
          });
}

function btnMake(afterNode, label, title, tag1_or_cb, tag2, noWrap) {
  var a = document.createElement('a');
  a.className = 'Button';
  a.style.setProperty('float','right');
  a.innerHTML = label;
  a.title = title;
  a.addEventListener('click',
            typeof(tag1_or_cb) == 'function'
                     ? tag1_or_cb
                     : noWrap ? function(e){edInsertText(tag1_or_cb, edInit(e.target))} 
                              : function(e){edWrapInTag(tag1_or_cb, tag2, edInit(e.target))});
  a.textAreaNode = afterNode.parentNode.textAreaNode;
  afterNode.parentNode.insertBefore(a, afterNode.nextElementSibling);
}

function edInit(btn) {
  var ed = {node: btn.textAreaNode || btn.parentNode.textAreaNode}
  ed.sel1 = ed.node.selectionStart;
  ed.sel2 = ed.node.selectionEnd,
  ed.text = ed.node.value;
  ed.sel = ed.text.substring(ed.sel1, ed.sel2);
  return ed;
}

function edWrapInTag(tag1, tag2, ed) {
  ed.node.value = ed.text.substr(0, ed.sel1) + tag1 + ed.sel + (tag2?tag2:tag1) + ed.text.substr(ed.sel2);
  ed.node.setSelectionRange(ed.sel1 + tag1.length, ed.sel1 + tag1.length + ed.sel.length);
  ed.node.focus();
}

function edInsertText(text, ed) {
  var ed = edInit(btn);
  ed.node.value = ed.text.substr(0, ed.sel2) + text + ed.text.substr(ed.sel2);
  ed.node.setSelectionRange(ed.sel2 + text.length, ed.sel2 + text.length);
  ed.node.focus();
}