Here you can find the source of toJSON()
Date.prototype.toJSON = function () { return moment(this).format().split("+")[0]; }
Date.prototype.toJSON = function() { var x = new Date(this); x.setHours(x.getHours() - x.getTimezoneOffset() / 60); return x.toISOString(); };
Date.prototype.toJSON = function() { return '"' + this.getUTCFullYear() + '-' + (this.getUTCMonth() + 1).toPaddedString(2) + '-' + this.getUTCDate().toPaddedString(2) + 'T' + this.getUTCHours().toPaddedString(2) + ':' + this.getUTCMinutes().toPaddedString(2) + ':' + this.getUTCSeconds().toPaddedString(2) + 'Z"'; };
Date.prototype.toJSON = function() { return '"' + this.getUTCFullYear() + '-' + (this.getUTCMonth() + 1).toPaddedString(2) + '-' + this.getUTCDate().toPaddedString(2) + 'T' + this.getUTCHours().toPaddedString(2) + ':' + this.getUTCMinutes().toPaddedString(2) + ':' + this.getUTCSeconds().toPaddedString(2) + 'Z"'; };
Date.prototype.toJSON = function() { return '"' + this.getUTCFullYear() + '-' + (this.getUTCMonth() + 1).toPaddedString(2) + '-' + this.getUTCDate().toPaddedString(2) + 'T' + this.getUTCHours().toPaddedString(2) + ':' + this.getUTCMinutes().toPaddedString(2) + ':' + this.getUTCSeconds().toPaddedString(2) + 'Z"'; };