Resize a base64 image with javascript

imgResize.js

const imgResize = (base64, factor) => {
    return new Promise((resolve, reject) => {
        const watchdog = setTimeout(()=>{
            reject(new Error("TIMEOUT"));
        }, 5000); // If image loading takes too long
        const canvas = document.createElement("canvas");                        
        const img = new Image();
        img.onload = function () {
            clearTimeout(watchdog);
            canvas.width = Math.round(img.width*factor);
            canvas.height = Math.round(img.height*factor);
            const ctx = canvas.getContext("2d");
            ctx.scale(factor, factor);  
            ctx.drawImage(img, 0, 0);
            resolve(canvas.toDataURL());
        };
        img.src = base64;
    });
};