index.js

const dateToIsoOrigin = Date.prototype.toISOString;
const ddFormat = (x) => (100 + Math.floor(Math.abs(x))).toString().slice(-2);
const jsonParseOrigin = JSON.parse;
const isoDatePattern = /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}[.Z:+\-\d]*?$/;
const dateonlyPattern = /^\d{4}-\d{2}-\d{2}$/;
const dotnetDatePattern = /^\/Date\((\d+)([+\-\d]*)\)\/$/;



/** @param {{dotnet?: boolean, dateonly?: boolean}} [options] */
export default function apply(options){
    options = { ...options };
    
    // serialization fix: preserve timezone information
    if (dateToIsoOrigin.call(new Date).slice(-1) == 'Z')
        Date.prototype.toJSON = function () {
            const offset = this.getTimezoneOffset();
            return [
                dateToIsoOrigin.call(new Date(this.getTime() - offset * 60000)).slice(0, -1),
                offset > 0 ? '-' : '+',
                ddFormat(offset / 60),
                ':',
                ddFormat(offset % 60),
            ].join('');
        };
    
    // deserialization fix: change date-string to date-object
    JSON.parse = (text, reviver) => jsonParseOrigin(text, (k, v) => {
        if (reviver)
            v = reviver(k, v);
    
        if (isoDatePattern.test(v))
            return new Date(v);

        if(options.dateonly && dateonlyPattern.test(v))
            return new Date(v + 'T00:00:00');
        
        let tmp; 
        if (options.dotnet && (tmp = dotnetDatePattern.exec(v)))
            return new Date(tmp.slice(1, 3).reduce((a, x) => a + (parseInt(x) || 0), 0));
    
        return v;
    });

    if (window.Response)
        Response.prototype.json = async function () {
            return JSON.parse(await this.text());
        }
};

apply();