pingpoliCandlestickChart.js

/*
A single-file JavaScript class to draw candlestick charts.
Use at your own risk.
https://twitter.com/pingpoli
https://pingpoli.de
*/
function pingpoliCandlestick( timestamp , open , close , high , low )
{
    this.timestamp = parseInt(timestamp); 
    this.open = parseFloat(open);
    this.close = parseFloat(close);
    this.high = parseFloat(high);
    this.low = parseFloat(low);
}



function pingpoliCandlestickChart( canvasElementID )
{
    this.canvas = document.getElementById( canvasElementID );
	this.width = parseInt( this.canvas.width );
	this.height = parseInt( this.canvas.height );
	this.context = this.canvas.getContext( "2d" );

    this.canvas.addEventListener( "mousemove" , ( e ) => {
        this.mouseMove( e );
    } );
    this.canvas.addEventListener( "mouseout" , ( e ) => {
        this.mouseOut( e );
    } );

    this.canvas.style.backgroundColor = "#252525";
    this.context.font = '12px sans-serif';
    this.gridColor = "#444444";
    this.gridTextColor = "#aaaaaa";
    this.mouseHoverBackgroundColor = "#eeeeee";
    this.mouseHoverTextColor = "#000000";
    this.greenColor = "#00cc00";
    this.redColor = "#cc0000";
    this.greenHoverColor = "#00ff00";
    this.redHoverColor = "#ff0000";

    this.context.lineWidth = 1;
    this.candleWidth = 5;

    this.marginLeft = 10;
    this.marginRight = 100;
    this.marginTop = 10;
    this.marginBottom = 30;

    this.yStart = 0;
    this.yEnd = 0;
    this.yRange = 0;
    this.yPixelRange = this.height-this.marginTop-this.marginBottom;

    this.xStart = 0;
    this.xEnd = 0;
    this.xRange = 0;
    this.xPixelRange = this.width-this.marginLeft-this.marginRight;

    // these are only approximations, the grid will be divided in a way so the numbers are nice
    this.xGridCells = 16;
    this.yGridCells = 16;

    this.b_drawMouseOverlay = false;
    this.mousePosition = { x: 0 , y: 0 };
    this.xMouseHover = 0;
    this.yMouseHover = 0;
    this.hoveredCandlestickID = 0;

    this.candlesticks = [];
}



pingpoliCandlestickChart.prototype.addCandlestick = function( candlestick )
{
    this.candlesticks.push( candlestick );
}



pingpoliCandlestickChart.prototype.mouseMove = function( e )
{
    var getMousePos = ( e ) =>
    {
        var rect = this.canvas.getBoundingClientRect();
        return { x: e.clientX-rect.left , y: e.clientY-rect.top };
    }
    this.mousePosition = getMousePos( e );
    this.mousePosition.x += this.candleWidth/2;
    this.b_drawMouseOverlay = true;
    if ( this.mousePosition.x < this.marginLeft ) this.b_drawMouseOverlay = false;
    if ( this.mousePosition.x > this.width-this.marginRight+this.candleWidth ) this.b_drawMouseOverlay = false;
    if ( this.mousePosition.y > this.height-this.marginBottom ) this.b_drawMouseOverlay = false;
    if ( this.b_drawMouseOverlay )
    {
        this.yMouseHover = this.yToValueCoords( this.mousePosition.y );
        this.xMouseHover = this.xToValueCoords( this.mousePosition.x );
        // snap to candlesticks
        var candlestickDelta = this.candlesticks[1].timestamp-this.candlesticks[0].timestamp;
        this.hoveredCandlestickID = Math.floor((this.xMouseHover-this.candlesticks[0].timestamp)/candlestickDelta);
        this.xMouseHover = Math.floor(this.xMouseHover/candlestickDelta)*candlestickDelta;
        this.mousePosition.x = this.xToPixelCoords( this.xMouseHover );
        this.draw();
    }
    else this.draw();
}



pingpoliCandlestickChart.prototype.mouseOut = function( e )
{
    this.b_drawMouseOverlay = false;
    this.draw();
}



pingpoliCandlestickChart.prototype.draw = function()
{
	// clear background
	this.context.clearRect( 0 , 0 , this.width , this.height );

    this.calculateYRange();
    this.calculateXRange();

    this.drawGrid();

    this.candleWidth = this.xPixelRange/this.candlesticks.length;
    this.candleWidth--;
    if ( this.candleWidth%2 == 0 ) this.candleWidth--;

    for ( var i = 0 ; i < this.candlesticks.length ; ++i )
    {
        var color = ( this.candlesticks[i].close > this.candlesticks[i].open ) ? this.greenColor : this.redColor;

        if ( i == this.hoveredCandlestickID )
        {
            if ( color == this.greenColor ) color = this.greenHoverColor;
            else if ( color == this.redColor ) color = this.redHoverColor;
        }

        // draw the wick
        this.drawLine( this.xToPixelCoords( this.candlesticks[i].timestamp ) , this.yToPixelCoords( this.candlesticks[i].low ) , this.xToPixelCoords( this.candlesticks[i].timestamp ) , this.yToPixelCoords( this.candlesticks[i].high ) , color );

        // draw the candle
        this.fillRect( this.xToPixelCoords( this.candlesticks[i].timestamp )-Math.floor( this.candleWidth/2 ) , this.yToPixelCoords( this.candlesticks[i].open ) , this.candleWidth , this.yToPixelCoords( this.candlesticks[i].close ) - this.yToPixelCoords( this.candlesticks[i].open ) , color );
    }

    // draw mouse hover
    if ( this.b_drawMouseOverlay )
    {
        // price line
        this.context.setLineDash( [5,5] );
        this.drawLine( 0 , this.mousePosition.y , this.width , this.mousePosition.y , this.mouseHoverBackgroundColor );
        this.context.setLineDash( [] );
        var str = this.roundPriceValue( this.yMouseHover );
        var textWidth = this.context.measureText( str ).width;
        this.fillRect( this.width-70 , this.mousePosition.y-10 , 70 , 20 , this.mouseHoverBackgroundColor );
        this.context.fillStyle = this.mouseHoverTextColor;
        this.context.fillText( str , this.width-textWidth-5 , this.mousePosition.y+5 );

        // time line
        this.context.setLineDash( [5,5] );
        this.drawLine( this.mousePosition.x , 0 , this.mousePosition.x , this.height , this.mouseHoverBackgroundColor );
        this.context.setLineDash( [] );
        str = this.formatDate( new Date( this.xMouseHover ) );
        textWidth = this.context.measureText( str ).width;
        this.fillRect( this.mousePosition.x-textWidth/2-5 , this.height-20 , textWidth+10 , 20 , this.mouseHoverBackgroundColor );
        this.context.fillStyle = this.mouseHoverTextColor;
        this.context.fillText( str , this.mousePosition.x-textWidth/2 , this.height-5 );

        // data
        var yPos = this.mousePosition.y-95;
        if ( yPos < 0 ) yPos = this.mousePosition.y+15;

        this.fillRect( this.mousePosition.x+15 , yPos , 100 , 80 , this.mouseHoverBackgroundColor );
        var color = ( this.candlesticks[this.hoveredCandlestickID].close > this.candlesticks[this.hoveredCandlestickID].open ) ? this.greenColor : this.redColor;
        this.fillRect( this.mousePosition.x+15 , yPos , 10 , 80 , color );
        this.context.lineWidth = 2;
        this.drawRect( this.mousePosition.x+15 , yPos , 100 , 80 , color );
        this.context.lineWidth = 1;

        this.context.fillStyle = this.mouseHoverTextColor;
        this.context.fillText( "O: "+this.candlesticks[this.hoveredCandlestickID].open , this.mousePosition.x+30 , yPos+15 );
        this.context.fillText( "C: "+this.candlesticks[this.hoveredCandlestickID].close , this.mousePosition.x+30 , yPos+35 );
        this.context.fillText( "H: "+this.candlesticks[this.hoveredCandlestickID].high , this.mousePosition.x+30 , yPos+55 );
        this.context.fillText( "L: "+this.candlesticks[this.hoveredCandlestickID].low , this.mousePosition.x+30 , yPos+75 );
    }
}



pingpoliCandlestickChart.prototype.drawGrid = function()
{
    // roughly divide the yRange into cells
    var yGridSize = (this.yRange)/this.yGridCells;

    // try to find a nice number to round to
    var niceNumber = Math.pow( 10 , Math.ceil( Math.log10( yGridSize ) ) );
    if ( yGridSize < 0.25 * niceNumber ) niceNumber = 0.25 * niceNumber;
    else if ( yGridSize < 0.5 * niceNumber ) niceNumber = 0.5 * niceNumber;

    // find next largest nice number above yStart
    var yStartRoundNumber = Math.ceil( this.yStart/niceNumber ) * niceNumber;
    // find next lowest nice number below yEnd
    var yEndRoundNumber = Math.floor( this.yEnd/niceNumber ) * niceNumber;

    for ( var y = yStartRoundNumber ; y <= yEndRoundNumber ; y += niceNumber )
    {
        this.drawLine( 0 , this.yToPixelCoords( y ) , this.width , this.yToPixelCoords( y ) , this.gridColor );
        var textWidth = this.context.measureText( this.roundPriceValue( y ) ).width;
        this.context.fillStyle = this.gridTextColor;
        this.context.fillText( this.roundPriceValue( y ) , this.width-textWidth-5 , this.yToPixelCoords( y )-5 );
    }

    // roughly divide the xRange into cells
    var xGridSize = (this.xRange)/this.xGridCells;

    // try to find a nice number to round to
    niceNumber = Math.pow( 10 , Math.ceil( Math.log10( xGridSize ) ) );
    if ( xGridSize < 0.25 * niceNumber ) niceNumber = 0.25 * niceNumber;
    else if ( xGridSize < 0.5 * niceNumber ) niceNumber = 0.5 * niceNumber;

    // find next largest nice number above yStart
    var xStartRoundNumber = Math.ceil( this.xStart/niceNumber ) * niceNumber;
    // find next lowest nice number below yEnd
    var xEndRoundNumber = Math.floor( this.xEnd/niceNumber ) * niceNumber;

    // if the total x range is more than 5 days, format the timestamp as date instead of hours
    var b_formatAsDate = false;
    if ( this.xRange > 60*60*24*1000*5 ) b_formatAsDate = true;

    for ( var x = xStartRoundNumber ; x <= xEndRoundNumber ; x += niceNumber )
    {
        this.drawLine( this.xToPixelCoords( x ) , 0 , this.xToPixelCoords( x ) , this.height , this.gridColor );
        var date = new Date( x );
        var dateStr = "";
        if ( b_formatAsDate )
        {
            var day = date.getDate();
            if ( day < 10 ) day = "0"+day;
            var month = date.getMonth()+1;
            if ( month < 10 ) month = "0"+month;
            dateStr = day+"."+month;
        }
        else
        {
            var minutes = date.getMinutes();
            if ( minutes < 10 ) minutes = "0"+minutes;
            dateStr = date.getHours()+":"+minutes;
        }
        this.context.fillStyle = this.gridTextColor;
        this.context.fillText( dateStr , this.xToPixelCoords( x )+5 , this.height-5 );
    }
}



pingpoliCandlestickChart.prototype.calculateYRange = function()
{
    for ( var i = 0 ; i < this.candlesticks.length ; ++i )
    {
        if ( i == 0 )
        {
            this.yStart = this.candlesticks[i].low;
            this.yEnd = this.candlesticks[i].high;
        }
        else
        {
            if ( this.candlesticks[i].low < this.yStart )
            {
                this.yStart = this.candlesticks[i].low;
            }
            if ( this.candlesticks[i].high > this.yEnd )
            {
                this.yEnd = this.candlesticks[i].high;
            }
        }
    }
    this.yRange = this.yEnd - this.yStart;
}



pingpoliCandlestickChart.prototype.calculateXRange = function()
{
    this.xStart = this.candlesticks[0].timestamp;
    this.xEnd = this.candlesticks[this.candlesticks.length-1].timestamp;
    this.xRange = this.xEnd - this.xStart;
}



pingpoliCandlestickChart.prototype.yToPixelCoords = function( y )
{
    return this.height - this.marginBottom - (y-this.yStart) * this.yPixelRange/this.yRange;
}



pingpoliCandlestickChart.prototype.xToPixelCoords = function( x )
{
    return this.marginLeft + (x-this.xStart) * this.xPixelRange/this.xRange;
}



pingpoliCandlestickChart.prototype.yToValueCoords = function( y )
{
    return this.yStart + ( this.height - this.marginBottom - y ) * this.yRange/this.yPixelRange;
}



pingpoliCandlestickChart.prototype.xToValueCoords = function( x )
{
    return this.xStart + ( x - this.marginLeft ) * this.xRange/this.xPixelRange;
}



pingpoliCandlestickChart.prototype.drawLine = function( xStart , yStart , xEnd , yEnd , color )
{
	this.context.beginPath();
    // to get a crisp 1 pixel wide line, we need to add 0.5 to the coords
	this.context.moveTo( xStart+0.5 , yStart+0.5 );
	this.context.lineTo( xEnd+0.5 , yEnd+0.5 );
	this.context.strokeStyle = color;
	this.context.stroke();
}



pingpoliCandlestickChart.prototype.fillRect = function( x , y , width , height , color )
{
	this.context.beginPath();
    this.context.fillStyle = color;
	this.context.rect( x , y , width , height );
	this.context.fill();
}



pingpoliCandlestickChart.prototype.drawRect = function( x , y , width , height , color )
{
	this.context.beginPath();
    this.context.strokeStyle = color;
	this.context.rect( x , y , width , height );
	this.context.stroke();
}



pingpoliCandlestickChart.prototype.formatDate = function( date )
{
    var day = date.getDate();
    if ( day < 10 ) day = "0"+day;
    var month = date.getMonth()+1;
    if ( month < 10 ) month = "0"+month;
    var hours = date.getHours();
    if ( hours < 10 ) hours = "0"+hours;
    var minutes = date.getMinutes();
    if ( minutes < 10 ) minutes = "0"+minutes;
    return day+"."+month+"."+date.getFullYear()+" - "+hours+":"+minutes;
}



pingpoliCandlestickChart.prototype.roundPriceValue = function( value )
{
    if ( value > 1.0 ) return Math.round( value*100 )/100;
    if ( value > 0.001 ) return Math.round( value*1000 )/1000;
    if ( value > 0.00001 ) return Math.round( value*100000 )/100000;
    if ( value > 0.0000001 ) return Math.round( value*10000000 )/10000000;
    else return Math.round( value*1000000000 )/1000000000;
}

Hi, do you know how you would increase performance for this when plotting large datasets? ie when plotting 50K+ candles, the graph grinds to a halt and performance really suffers.