An Ext JS 4 grid plugin that provides Microsoft Excel-esque cell navigation and editing via keyboard.

excel-grid-plugin.js

var newGridCellValue = '',
    deleteGridCellValue = false;

Ext.define('ExcelCellEditing', {
    extend: 'Ext.grid.plugin.CellEditing',
    alias: 'plugin.excelcellediting',

    initEditTriggers: function () {
        var me = this;

        var keys = [];
        for (var i = 48; i < 58; i++) { keys.push(i); } // 0-9
        for (var i = 65; i < 91; i++) { keys.push(i); } // A-Z
        for (var i = 97; i < 123; i++) { keys.push(i); } // a-z

        // listen for particular key presses made over cells
        me.view.addListener('render', function () {
            var keyPressMap = new Ext.util.KeyMap({
                target: me.view.el,
                eventName: 'keypress',
                binding: [{
                    key: keys,
                    handler: me.onAlphaNumericKey,
                    scope: me
                }]
            });

            var keyDownMap = new Ext.util.KeyMap({
                target: me.view.el,
                eventName: 'keydown',
                binding: [{
                    key: Ext.EventObject.DELETE,
                    handler: me.onDeleteKey,
                    scope: me
                }, {
                    key: Ext.EventObject.BACKSPACE,
                    handler: me.onBackspaceKey,
                    scope: me
                }]
            });

        }, me, { single: true });

        me.callParent(arguments);
    },
    onAlphaNumericKey: function (keyCode, e) { // only executes before a cell has entered edit mode
        var me = this,
            grid = me.grid,
            pos = grid.getSelectionModel().getCurrentPosition(),
            record = grid.store.getAt(pos.row),
            columnHeader = grid.headerCt.getHeaderAtIndex(pos.column);

        if (me.getEditor(record, columnHeader)) {
            // insert the key pressed into the editor field and start editing
            newGridCellValue = String.fromCharCode(keyCode);
            me.startEdit(record, columnHeader);
        }
    },
    onBackspaceKey: function (keyCode, e) { // only executes before a cell has entered edit mode
        var me = this;

        e.stopEvent(); // cancel the default browser behaviour of navigating one page back
        me.onDeleteKey(keyCode, e);
    },
    onDeleteKey: function (keyCode, e) { // only executes before a cell has entered edit mode
        var me = this,
            grid = me.grid,
            pos = grid.getSelectionModel().getCurrentPosition(),
            record = grid.store.getAt(pos.row),
            columnHeader = grid.headerCt.getHeaderAtIndex(pos.column);

        if (me.getEditor(record, columnHeader)) {
            // perform an "instantaneous" edit that essentially just sets the value of the cell to nothing
            deleteGridCellValue = true;
            me.startEdit(record, columnHeader);
        }
    },
    onEnterKey: function (e) { // only executes before a cell has entered edit mode
        var me = this,
            grid = me.grid,
            sm = grid.getSelectionModel();

        me.callParent(arguments);

        // cellmodel navigates left/right when tab key is pressed by default, but not up/down when enter is pressed
        // the code below enables this functionality for cells that are not editable
        if (!grid.headerCt.getHeaderAtIndex(sm.getCurrentPosition().column).getEditor()) {
            sm.move(e.shiftKey ? 'up' : 'down', e);
        }
    },
    onSpecialKey: function (ed, field, e) { // only executes when a cell is in edit mode
        var me = this,
            sm = me.grid.getSelectionModel();

        // cellmodel navigates left/right when tab key is pressed by default, but not up/down when enter is pressed
        // the code below enables this functionality for cells that are editable
        if (e.getKey() === e.ENTER) {
            me.addListener('edit', function () {
                sm.move(e.shiftKey ? 'up' : 'down', e); // navigate up/down once edit completes
            }, me, { single: true });
        }

        me.callParent(arguments);
    }
});

/**
*  The following override allows for keys pressed over a grid cell that isn't yet in edit mode to be persisted into
*  the cell once edit mode activates. It does this by getting the value of a temporary global variable that is set
*  by the cell editing plugin above.
*/
Ext.override(Ext.Editor, {
    startEdit: function (el, value) {
        var me = this,
            field = me.field;

        me.completeEdit();
        me.boundEl = Ext.get(el);
        value = Ext.isDefined(value) ? value : me.boundEl.dom.innerHTML;

        if (!me.rendered) {
            me.render(me.parentEl || document.body);
        }

        if (me.fireEvent('beforestartedit', me, me.boundEl, value) !== false) {
            me.startValue = value;
            me.show();
            field.reset();

            if (deleteGridCellValue) {
                field.setValue('');
                me.editing = true;
                me.completeEdit();
                deleteGridCellValue = false; // reset global variable
            }
            else {
                if (newGridCellValue == '') {
                    // default behaviour of Ext.Editor (see source if needed)
                    field.setValue(value);
                }
                else {
                    // custom behaviour to handle an alphanumeric key press from non-edit mode
                    field.setRawValue(newGridCellValue);
                    newGridCellValue = ''; // reset global variable
                    
                    if (field instanceof Ext.form.field.ComboBox) {
                    	// force the combo box's filtered dropdown list to be displayed (some browsers need this)
                    	field.doQueryTask.delay(field.queryDelay);
                    }
                }

                me.realign(true);
                field.focus(false, 10);
                if (field.autoSize) {
                    field.autoSize();
                }
                me.editing = true;
            }
        }
    }
});

/**
*  The following override fixes a quirk in Internet Explorer where the text cursor/caret is positioned at the beginning
*  of a cell's field the first time its editor is activated. The quirk makes instant grid cell editing on keypress difficult,
*  because the caret gets positioned BEFORE text already in the cell, causing the user to prepend text rather than append.
*/
Ext.override(Ext.dom.Element, {
    focus: function (defer, dom) {
        var me = this,
            dom = dom || me.dom;

        try {
            if (Number(defer)) {
                Ext.defer(me.focus, defer, me, [null, dom]);
            } else {
                dom.focus();

                // start override
                dom.value = dom.value;
                dom.focus();
                if (dom.sof) {
                    dom.select();
                }
                // end override
            }
        } catch (e) { }

        return me;
    }
});