Converting object to form data in angular

http.helper.ts

export class HttpHelper {
    static getObjectToFormData(obj: any): FormData {
        const formData = new FormData();
        for (var key in obj) {
            if (typeof (obj[key]) === 'string' || typeof (obj[key]) === 'number') {
                formData.append(key, obj[key])
            }
            else if (obj[key] && obj[key] instanceof Date) {
                formData.append(key, obj[key].toLocaleDateString())
            }
            else if (obj[key] instanceof File) {
                formData.append(key, obj[key], obj[key].name);
            }
            else if (obj[key] instanceof FileList) {
                for (let i = 0; i < obj[key].length; i++) {
                    const file = obj[key][i];
                    formData.append(`${key}`, file, file.name);
                }
            }
            else if (obj[key] && typeof (obj[key]) === 'object') {
                this.objToFormDataRecursive(key, obj[key], formData);
            }
        }
        return formData;
    }

    private static objToFormDataRecursive(formKey: string, obj: any, formData: FormData): any {
        for (var key in obj) {
            if (typeof (obj[key]) === 'string' || typeof (obj[key]) === 'number') {
                formData.append(`${formKey}[${key}]`, obj[key])
            }
            else if (obj[key] && obj[key] instanceof Date) {
                formData.append(key, obj[key].toLocaleDateString())
            }
            else if (obj[key] instanceof File) {
                formData.append(`${formKey}[${key}]`, obj[key]);
            }
            else if (obj[key] instanceof FileList) {
                for (var i = 0; i < obj[key].length; i++) {
                    const file = obj[key][i];
                    formData.append(`${formKey}[${key}]`, file, file.name);
                }
            }
            else if (obj[key] && typeof (obj[key]) === 'object') {
                return this.objToFormDataRecursive(`${formKey}[${key}]`, obj[key], formData);
            }
        }
    }
}