Function map

static/editor.md/lib/codemirror/lib/codemirror.js:8078–8082

(array, f)

    return -1;
  }
  function map(array, f) {
    var out = [];
    for (var i = 0; i < array.length; i++) out[i] = f(array[i], i);
    return out;
  }

  function nothing() {}