CodeMirror: Breakpoint demo

var editor = CodeMirror.fromTextArea(document.getElementById("code"), {

  lineNumbers: true,

  gutters: ["CodeMirror-linenumbers", "breakpoints"]

});

editor.on("gutterClick", function(cm, n) {

  var info = cm.lineInfo(n);

  cm.setGutterMarker(n, "breakpoints", info.markers ? null : makeMarker());

});

function makeMarker() {

  var marker = document.createElement("div");

  marker.innerHTML = "●";

  marker.className = "breakpoint";

  return marker;

}