Preserving the 'this' context in image.onload using JavaScript

Other Questions JavaScript
1

In the provided code snippet, an ‘InfoImage’ constructor initializes an image and attempts to retrieve its dominant color and pixel information in the ‘onload’ event. However, referencing ‘this’ inside the ‘img.onload’ function inadvertently points to the image context instead of the ‘InfoImage’ object. How can I adjust the code to ensure that ‘color’ and ‘maxPixels’ are saved within the ‘InfoImage’ instance? Here’s a modified example:

function ImageDetails(imagePath, imageTitle) {
    this.imagePath = imagePath;
    this.imageTitle = imageTitle;
    this.primaryColor = null;
    this.pixelCount = null;

    this.setup = function() {
        var drawingCanvas = document.querySelector("canvas");
        var colorAnalyzer = new ColorAnalyzer(drawingCanvas);
        var newImage = new Image();
        newImage.onload = () => {
            colorAnalyzer.initialize(newImage);
            this.primaryColor = colorAnalyzer.calculateDominantColor();
            this.pixelCount = colorAnalyzer.calculateColorPixels();
        };
        newImage.src = this.imagePath;
    };

    this.setup();
}
2

To keep the context of this, use an arrow function in the onload event:

function ImageDetails(imagePath, imageTitle) {
    this.imagePath = imagePath;
    this.imageTitle = imageTitle;
    this.primaryColor = null;
    this.pixelCount = null;

    this.setup = function() {
        const drawingCanvas = document.querySelector("canvas");
        const colorAnalyzer = new ColorAnalyzer(drawingCanvas);
        const newImage = new Image();
        newImage.onload = () => {
            colorAnalyzer.initialize(newImage);
            this.primaryColor = colorAnalyzer.calculateDominantColor();
            this.pixelCount = colorAnalyzer.calculateColorPixels();
        };
        newImage.src = this.imagePath;
    };

    this.setup();
}