Cell Renderer

The job of the grid is to lay out the cells. By default the grid will create the cell values using simple text. If you want more complex HTML inside the cells you can achieve this using cell renderers.

This page explains first how to create cell renderers using standard JavaScript. It then continues on how to create cell renderers using components of different frameworks (e.g. how to create a cell renderer using a React or Angular component). If you intend to use the framework variant, you should first read the JavaScript sections as the framework sections build on this.

Simple Cell Renderer Example

The example below shows a simple cell renderer in action. It uses a cell renderer to show a hash (#) symbol instead of the medal count.

Cell Renderer Component

The interface for the cell renderer component is as follows:

interface ICellRendererComp {
    // Optional - Params for rendering. The same params that are passed to the cellRenderer function.
    init?(params: ICellRendererParams): void;

    // Mandatory - Return the DOM element of the component, this is what the grid puts into the cell
    getGui(): HTMLElement;

    // Optional - Gets called once by grid after rendering is finished - if your renderer needs to do any cleanup,
    // do it here
    destroy?(): void;

    // Mandatory - Get the cell to refresh. Return true if the refresh succeeded, otherwise return false.
    // If you return false, the grid will remove the component from the DOM and create
    // a new component in its place with the new values.
    refresh(params: ICellRendererParams): boolean;
}

The interface for the cell renderer parameters is as follows:

interface ICellRendererParams {
    value: any, // value to be rendered
    valueFormatted: any, // value to be rendered formatted
    getValue: () => any, // convenience function to get most recent up to date value
    setValue: (value: any) => void, // convenience to set the value
    formatValue: (value: any) => any, // convenience to format a value using the column's formatter
    data: any, // the row's data
    node: RowNode, // row node
    colDef: ColDef, // the cell's column definition
    column: Column, // the cell's column
    rowIndex: number, // the current index of the row (this changes after filter and sort)
    api: GridApi, // the grid API
    eGridCell: HTMLElement, // the grid's cell, a DOM div element
    eParentOfValue: HTMLElement, // the parent DOM item for the cell renderer, same as eGridCell unless using checkbox selection
    columnApi: ColumnApi, // grid column API
    context: any, // the grid's context
    refreshCell: () => void // convenience function to refresh the cell
}

Below is a simple example of cell renderer class:

// function to act as a class
function MyCellRenderer () {}

// gets called once before the renderer is used
MyCellRenderer.prototype.init = function(params) {
    // create the cell
    this.eGui = document.createElement('div');
    this.eGui.innerHTML = '<span class="my-css-class"><button class="btn-simple">Push Me</button><span class="my-value"></span></span>';

    // get references to the elements we want
    this.eButton = this.eGui.querySelector('.btn-simple');
    this.eValue = this.eGui.querySelector('.my-value');

    // set value into cell
    this.eValue.innerHTML = params.valueFormatted ? params.valueFormatted : params.value;

    // add event listener to button
    this.eventListener = function() {
        console.log('button was clicked!!');
    };
    this.eButton.addEventListener('click', this.eventListener);
};

// gets called once (assuming destroy hasn't been called first) when grid ready to insert the element
MyCellRenderer.prototype.getGui = function() {
    return this.eGui;
};

// gets called whenever the user gets the cell to refresh
MyCellRenderer.prototype.refresh = function(params) {
    // set value into cell again
    this.eValue.innerHTML = params.valueFormatted ? params.valueFormatted : params.value;
    // return true to tell the grid we refreshed successfully
    return true;
};

// gets called when the cell is removed from the grid
MyCellRenderer.prototype.destroy = function() {
    // do cleanup, remove event listener from button
    if (this.eButton) {
        // check that the button element exists as destroy() can be called before getGui()
        this.eButton.removeEventListener('click', this.eventListener);
    }
};

Registering Cell Renderers with Columns

See the section registering custom components for details on registering and using custom cell renderers.

Component Refresh

Component refresh needs a bit more explanation. Here we go through some of the finer details.

Events Causing Refresh

The grid can refresh the data in the browser, but not every refresh / redraw of the grid results in the refresh method of your cell renderer getting called. The following items are those that do cause refresh to be called:

• Calling rowNode.setDataValue(colKey, value) to set a value directly onto the rowNode. This is the preferred API way to change one value from outside of the grid.
• When editing a cell and editing is stopped, so that cell displays new value after editing.
• Calling api.refreshCells() to inform grid data has changed (see Refresh).

If any of the above occur and the grid confirms the data has changed via Change Detection, then the refresh() method will be called.

The following will not result in the cell renderer's refresh method being called:

• Calling rowNode.setData(data) to set new data into a rowNode. When you set the data for the whole row, the whole row in the DOM is recreated again from scratch.
• Scrolling the grid vertically causes columns (and their containing cells) to be removed and inserted due to column virtualisation.

All of the above will result in the component being destroyed and recreated.

Change Detection

As mentioned in the section on Change Detection, the refresh of the cell will not take place if the value getting rendered has not changed.

Grid vs Component Refresh

The refresh method returns back a boolean value. If you do not want to handle the refresh in the cell renderer, just return back false from an otherwise empty method. This will indicate to the grid that you did not refresh and the grid will instead destroy the component and create another instance of your component from scratch instead.

Cell Renderer Component Lifecycle

The lifecycle of the cell renderer is as follows:

• new is called on the class.
• init() is called once.
• getGui() is called 0 or 1 times (destroy could get called first, i.e. when scrolling quickly)
• refresh() is called 0...n times (i.e. it may never be called, or called multiple times)
• destroy() is called once.

In other words, new(), init() and destroy() are always called exactly once. getGui() will typically get called once unless destroy() is called first. refresh() is optionally called multiple times.

If you are doing refresh(), remember that getGui() is only called once (assuming the cell renderer hasn't been destroyed first), so be sure to update the existing GUI in your refresh, do not think that the grid is going to call getGui() again to get a new version of the GUI.

Cell Rendering Flow

The diagram below (which is taken from the section Value Getters & Formatters) summarises the steps the grid takes while working out what to render and how to render.

In short, a value is prepared. The value comes using either the colDef.field or the colDef.valueGetter. The value is also optionally passed through a colDef.valueFormatter if it exists. Then the value is finally placed into the DOM, either directly, or by using the chosen colDef.cellRenderer.

Complementing Cell Renderer Params

On top of the parameters provided by the grid, you can also provide your own parameters. This is useful if you want to 'configure' your cell renderer. For example, you might have a cell renderer for formatting currency but you need to provide what currency for your cell renderer to use.

Provide params to a cell renderer using the colDef option cellRendererParams.

// define cellRenderer to be reused
var myCellRenderer = function(params) {
    return '<span style="color: ' + params.color + '">' + params.value + '</span>';
}

// use with a colour
colDef.cellRenderer = myCellRenderer;
colDef.cellRendererParams = {
    color: 'guinnessBlack'
}

// use with another colour
colDef.cellRenderer = myCellRenderer;
colDef.cellRendererParams = {
    color: 'irishGreen'
}

Data in Cell Renderers

Sometimes the data property in the parameters given to a cell renderer might not be populated. This can happen for example when using row grouping (where the row node has aggData and groupData instead of data), or when rows are being loaded in the Infinite Row Model and do not yet have data. It is best to check that data does exist before accessing it in your cell renderer, for example:

colDef.cellRenderer = function(params) {
    // check the data exists, to avoid error
    if (params.data) {
        // data exists, so we can access it
        return '**' + params.data.theBoldValue + '**';
    }
    // when we return null, the grid will display a blank cell
    return null;
};

Cell Renderer Function

Instead of using a component, it's possible to use a simple function for a cell renderer. The function takes the same parameters as the cell renderer init method in the component variant. The function should return back either a) a string of HTML or b) a DOM object.

Use the function variant of a cell renderer if you have no refresh or cleanup requirements (ie you don't need to implement the refresh or destroy functions).

If using a framework such as React or Angular for your cell renderers then you must provide a cell renderer component. There is no function equivalent for the frameworks such as React and Angular.

Below are some simple examples of cell renderers provided as simple functions:

// put the value in bold
colDef.cellRenderer = function(params) {
    return '**' + params.value.toUpperCase() + '**';
}

// put a tooltip on the value
colDef.cellRenderer = function(params) {
    return '<span title="the tooltip">' + params.value + '</span>';
}

// create a DOM object
colDef.cellRenderer = function(params) {
    var eDiv = document.createElement('div');
    eDiv.innerHTML = '<span class="my-css-class"><button class="btn-simple">Push Me</button></span>';
    var eButton = eDiv.querySelectorAll('.btn-simple')[0];

    eButton.addEventListener('click', function() {
        console.log('button was clicked!!');
    });

    return eDiv;
}

Complex Cell Renderer Example

The example below shows five columns formatted, demonstrating each of the methods above.

• 'Month' column uses cellStyle to format each cell in the column with the same style.
• 'Max Temp' and 'Min Temp' columns uses the Function method to format each cell in the column with the same style.
• 'Days of Air Frost' column uses the Component method to format each cell in the column with the same style
• 'Days Sunshine' and 'Rainfall (10mm)' use simple functions to display icons.

Accessing Cell Renderer Instances

After the grid has created an instance of a cell renderer for a cell it is possible to access that instance. This is useful if you want to call a method that you provide on the cell renderer that has nothing to do with the operation of the grid. Accessing cell renderers is done using the grid API getCellRendererInstances(params).

// function takes params to identify which cells and returns back a list of cell renderers
function getCellRendererInstances(params: GetCellRendererInstancesParams): ICellRendererComp[];

// params object for the above
interface GetCellRendererInstancesParams {
    // an optional list of row nodes
    rowNodes?: RowNode[];
    // an optional list of columns
    columns?: (string | Column)[];
}

An example of getting the cell renderer for exactly one cell is as follows:

// example - get cell renderer for first row and column 'gold'
var firstRowNode = gridOptions.api.getDisplayedRowAtIndex(0);
var params = { columns: ['gold'], rowNodes: [firstRowNode] };
var instances = gridOptions.api.getCellRendererInstances(params);

if (instances.length > 0) {
    // got it, user must be scrolled so that it exists
    var instance = instances[0];
}

Not that this method will only return instances of the cell renderer that exists. Due to row and column virtualisation, renderers will only exists for the user can actually see due to horizontal and vertical scrolling.

The example below demonstrates custom methods on cell renderers called by the application. The following can be noted:

• The medal columns are all using the user defined MedalCellRenderer. The cell renderer has an arbitrary method medalUserFunction() which prints some data to the console.
• The Gold method executes a method on all instances of the cell renderer in the gold column.
• The First Row Gold method executes a method on the gold cell of the first row only. Note that the getCellRendererInstances() method will return nothing if the grid is scrolled past the first row.
• The All Cells method executes a method on all instances of all cell renderers.

If your are using a framework component (detailed below), then the returned object is a wrapper and you can get the underlying cell renderer using getFrameworkComponentInstance()

// example - get cell renderer for first row and column 'gold'
var firstRowNode = gridOptions.api.getDisplayedRowAtIndex(0);
var params = { columns: ['gold'], rowNodes: [firstRowNode] };
var instances = gridOptions.api.getCellRendererInstances(params);

if (instances.length > 0) {
    // got it, user must be scrolled so that it exists
    var wrapperInstance = instances[0];
    var frameworkInstance = wrapperInstance.getFrameworkComponentInstance();
}

Cell Rendering

It is possible to provide Angular cell renderers for ag-Grid to use if you are are using the Angular version of ag-Grid. See registering framework components for how to register framework components.

Example: Rendering using Angular Components

Methods / Lifecycle

Your components need to implement AgRendererComponent. The ag Framework expects to find the agInit method on the created component, and uses it to supply the cell params.

All of the methods in the ICellRenderer interface described above are applicable to the Angular Component with the following exceptions:

• init() is not used. Instead implement the agInit method (on the AgRendererComponent interface).
• destroy() is not used. Instead implement the AngularOnDestroy interface (ngOnDestroy) for any cleanup you need to do.
• getGui() is not used. Instead do normal Angular magic in your Component via the Angular template.

Handling Refresh

To handle refresh, implement logic inside the refresh() method inside your component and return true. If you do not want to handle refresh, just return false from the refresh method (which | will tell the grid you do not handle refresh and your component will be destroyed and recreated if the underlying data changes).

Example: Rendering using more complex Components

Using more complex Angular Components in the Cell Renderers - specifically how you can use nested NgModule's within the grid.