Utilizing a TypeScript function to trigger an action from within a Chart.js option callback

Question

Utilizing a TypeScript function to trigger an action from within a Chart.js option callback

Currently, I am utilizing a wrapper for Chart.js that enables an animation callback to signify when the chart has finished drawing.

The chart options in my code are set up like this:

public chartOptions: any = {
    animation: {
        duration: 2000,
        onComplete: function () {
            //alert('anim complete');
            this.chartTestMethod();
        }
    },
    responsive: true
};

In addition, my chartTestMethod() is structured as follows:

chartTestMethod() {
     console.log('chartTestMethod called.');
}

I am aiming for the chartTestMethod() method to be invoked once the chart animation has completed. However, upon reaching that line of code after the animation finishes, I encounter the following error:

TypeError: this.chartTestMethod is not a function.

In essence, I am seeking guidance on how to effectively call that method. Any insights would be greatly appreciated!

javascript charts typescript angular chart.js

Answer 1

Answer №1

It appears that the chartTestMethod is located in the same class as chartOptions since it is being used under the context of this. It is important to grasp how JavaScript (and TypeScript, which extends JavaScript) handles the concept of this. There are numerous resources available for further exploration.

Assuming no prior knowledge of Chart.js, it seems unlikely that the this reference aligns with your class instance during the invocation of onComplete. Therefore, utilizing an arrow function would be more appropriate, like so:

onComplete: () => { this.chartTestMethod(); }

Research TypeScript arrow functions to ensure that this actually points to the intended instance.

Answer 2

It appears that the chartTestMethod is located in the same class as chartOptions since it is being used under the context of this. It is important to grasp how JavaScript (and TypeScript, which extends JavaScript) handles the concept of this. There are numerous resources available for further exploration.

Assuming no prior knowledge of Chart.js, it seems unlikely that the this reference aligns with your class instance during the invocation of onComplete. Therefore, utilizing an arrow function would be more appropriate, like so:

onComplete: () => { this.chartTestMethod(); }

Research TypeScript arrow functions to ensure that this actually points to the intended instance.

Answer 3

Answer №2

An error occurred because the reference to this is pointing to the object where the function is being executed. In this particular case, this is referring to the any.animation object which does not have a key named chartTestMethod. To resolve this issue, it depends on where the chartTestMethod method is defined. If it is defined in the global scope, you can simply remove the this keyword from your code.

function chartTestMethod(){
    console.log('chartTestMethod called.');
}

any = {
    animation: {
        duration: 2000,
        onComplete: function (){
            chartTestMethod();
        }
    },
    responsive: true
};

If you prefer to keep the method within the same object, you can structure your code like this:

any = {
    animation: {
        duration: 2000,
        onComplete: function (){
            this.chartTestMethod();
        },
        chartTestMethod: function(){
            console.log('chartTestMethod called.');
      }
    },
    responsive: true
};

Answer 4

An error occurred because the reference to this is pointing to the object where the function is being executed. In this particular case, this is referring to the any.animation object which does not have a key named chartTestMethod. To resolve this issue, it depends on where the chartTestMethod method is defined. If it is defined in the global scope, you can simply remove the this keyword from your code.

function chartTestMethod(){
    console.log('chartTestMethod called.');
}

any = {
    animation: {
        duration: 2000,
        onComplete: function (){
            chartTestMethod();
        }
    },
    responsive: true
};

If you prefer to keep the method within the same object, you can structure your code like this:

any = {
    animation: {
        duration: 2000,
        onComplete: function (){
            this.chartTestMethod();
        },
        chartTestMethod: function(){
            console.log('chartTestMethod called.');
      }
    },
    responsive: true
};

Answer 5

Answer №3

Utilize the bind(this) method

declare public chartOptions as any = {
    animation: {
        duration: 2000,
        onComplete: function () {
            //alert('anim complete');
            this.chartTestMethod();
        }.bind(this)
    },
    responsive: true
};

Answer 6

Utilize the bind(this) method

declare public chartOptions as any = {
    animation: {
        duration: 2000,
        onComplete: function () {
            //alert('anim complete');
            this.chartTestMethod();
        }.bind(this)
    },
    responsive: true
};

Utilizing a TypeScript function to trigger an action from within a Chart.js option callback

Answer №1

Answer №2

Answer №3

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