jupyter_contrib_nbextensions/usability/shift-tab.js

// assign dedent to shift-tab 

var shift_tab_extension = (function() {

    var dedentKey = { "Shift-Tab":"indentLess" };
    var key   = IPython.keyboard.keycodes;
    
    /**
     * Concatenate associative array objects
     *
     * Source: http://stackoverflow.com/questions/2454295/javascript-concatenate-properties-from-multiple-objects-associative-array
     */
    function collect() {
    var ret = {};
    var len = arguments.length;
    for (var i=0; i<len; i++) {
        for (p in arguments[i]) {
            if (arguments[i].hasOwnProperty(p)) {
                ret[p] = arguments[i][p];
            }
        }
    }
    return ret;
}

    /**
     * Intercept codemirror onKeyEvent in codecell
     *
     * @return {Boolean} returns false if hotkey is found, otherwise call original function
     */
    var intercept_codemirror_keyevent = function (cm, event) {
        /* Dummy for shift+Tab, who knows why */
        if (event.type == 'keydown' && event.which == key.tab && event.shiftKey) {
            return false;
        };
        return this.handle_codemirror_keyevent(cm,event);
    }

    function assign_key(cell) {
        var keys = cell.code_mirror.getOption('extraKeys');
        cell.code_mirror.setOption('onKeyEvent',$.proxy(intercept_codemirror_keyevent,cell));
        cell.code_mirror.setOption('extraKeys', collect(keys, dedentKey ));  
    }
    
    /**
     * Initialize newly created cell
     *
     * @param {Object} event
     * @param {Object} nbcell notebook cell
     */
    create_cell = function (event,nbcell,nbindex) {
        var cell = nbcell.cell;
        if ((cell instanceof IPython.CodeCell)) { assign_key(cell); }
    };

    /**
     * Initialize all cells
     *
     */
    var cells = IPython.notebook.get_cells();
    for(var i in cells){
        var cell = cells[i];
        if ((cell instanceof IPython.CodeCell)) { assign_key(cell); }
    };

    $([IPython.events]).on('create.Cell',create_cell);
})();