Javascript Utilities

Charba provides out of the box some utilities that you can use in your code.

info

The javascript utilities can be used even if the Charba.enable or DeferredCharba.enable are not called because they don't depend on CHART.JS.

Scheduler

The scheduler utility executes a particular block of code once after a specified time has elapsed.

The logic that you pass to the scheduler will run at some point in the future.

// creates and submits my task
// without any delay
CScheduler.get().submit(new Runnable(){

    @Override
    public void run(){
        // my logic
    }
    
});
// creates and submits my task
// waiting for 5 seconds
CScheduler.get().submit(new Runnable(){

    @Override
    public void run(){
        // my logic
    }
    
}, 5000);

Timer

The timer utility executes a particular block of code repeatedly at no less than the number of milliseconds.

// creates a timer with user logic
// and an interval of 5 seconds.
// the logic will run repeatedly
// every 5 seconds
CTimer timer = new CTimer(new Runnable(){

    @Override
    public void run(){
        // my logic
    }
    
}, 5000);
// starts timer
timer.start();

Starting

A timer will execute a particular block of code repeatedly after it has been started.

// starts timer
timer.start();

You can change the interval of an existing timer, restarting it with new interval to use:

// starts timer
// changing the interval 
// setting to 10 seconds
timer.start(10000);

Stopping

A timer can be stopped when you want to stop temporarily the execution or if it's not needed anymore.

// stops timer
timer.stop();

Chart auto update

In order to keep the chart up to date, you sometimes want to perform an update periodically. You might want to run a poll to the server for new data and update the chart.

The chart provides a method to configure the timer for the chart instance.

The timer will start executing the block of code repeatedly after the chart drawing and will e stopped when chart will be destroyed.

// creates the chart
LineChart chart = new LineChart();
// configures the timer
// to execute my code every 10 seconds 
chart.createAndSetTimer(new ChartTimerTask(){

    /**
     * Executes the task repeatedly, internally by the chart instance. 
     * 
     * @param chart chart instance
     */
    @Override
    public void execute(IsChart chart){
        // retrieves data from host
        // adds new data to chart
        // updates chart
        chart.update();
    }

}, 10000);

The chart needs a specific task interface to apply the logic.

The chart provides the access in order to stop and start the timer when you need.

// creates the chart
LineChart chart = new LineChart();
// gets timer
CTimer timer = chart.getTimer();
// checks if consistent
// because it could be null
if (timer != null){
    // stops the timer
    timer.stop();
}

Window

Charba provides a JavaScript window wrapper.

JavaScript Window is a global variable, representing the window in which the script is running.

Some methods are mapped in order to be executed in your GWT or J2CL project.

// gets device pixel ratio
double devicePixelRatio = Window.getDevicePixelRatio();

Console

One of the method of Window object, returns the console.

Charba provides the console object as shortcut to that window service.

The console provides access to the browser's debugging console. The specifics of how it works varies from browser to browser, but there is a de facto set of features that are typically provided.

// emits the log string 
Console.log("This is my log");
// emits the javascript objects
Console.log(object1, object2, object3);

JSON

The JSON object contains methods for converting objects to JSON and JSON string to objects.

Charba provides an implementation with the methods and capabilities to use in your GWT or J2CL project.

// gets and logs the object in JSON format
Console.log(JSON.stringify(object));
// gets and logs the object in JSON format
// with 3 spaces for indentation
Console.log(JSON.stringify(object, 3));
// creates and logs an object parsed by 
// a text in JSON format
Console.log(JSON.parse("{ test: 8, doc: true}", 3));

Regular expressions

Regular expressions are patterns used to match character combinations in strings.

Charba provides an implementation with a subset of methods and capabilities to use in your GWT or J2CL project.

// gets a string to check
String id = "myId"
// creates a regular expression
RegExp regExp = new RegExp("^[a-zA-Z0-9_-]+$");
// executes the regular expression
RegExpResult regExpResult = regExp.exec(id);
// checks if regular expression matches
if (regExpResult != null){
    // regular expression matches!
} else {
    // regular expression does NOT match!
}