Angular JSON object to query string

query-string-builder.ts

import {HttpParams} from "@angular/common/http";

export class QueryStringBuilder {

    static buildParametersFromSearch<T>(obj: T): HttpParams {
        let params: HttpParams= new HttpParams();

        if (obj == null)
        {
            return params;
        }

        return QueryStringBuilder.populateSearchParams(params, '', obj);
    }

    private static populateArray<T>(params: HttpParams, prefix: string, val: Array<T>): HttpParams {
        for (let index in val) {
            let key = prefix + '[' + index + ']';
            let value: any = val[index];
            params = QueryStringBuilder.populateSearchParams(params, key, value);
        }
        return params;
    }

    private static populateObject<T>(params: HttpParams, prefix: string, val: T): HttpParams {
        const objectKeys = Object.keys(val) as Array<keyof T>;

        for (let objKey of objectKeys) {

            let value = val[objKey];
            let key = prefix;
            if (prefix) {
                key += '[' + objKey + ']';
            } else {
                key += objKey;
            }

            params = QueryStringBuilder.populateSearchParams(params, key, value);
        }
        return params;
    }

    private static populateSearchParams<T>(params: HttpParams, key: string, value: any): HttpParams {
        if (value instanceof Array) {
            return QueryStringBuilder.populateArray(params, key, value);
        }
        else if (value instanceof Date) {
            return params.append(key, value.toISOString());
        }
        else if (value instanceof Object) {
            return QueryStringBuilder.populateObject(params, key, value);
        }
        else if ('undefined' !== typeof value && null !== value){
            return params.append(key, value.toString());
        }
        return params;
    }
}

Usage:

const data = {customUser: {firstName: 'john', lastName: 'doe', address: {street: 'wall street'}}, values: [0,1,2]}`;
let params = QueryStringBuilder.buildParametersFromSearch(data);

this.http.post(API_URL, params);

Posted data will be:

or as encoded:
customUser%5BfirstName%5D=john&customUser%5BlastName%5D=doe&customUser%5Baddress%5D%5Bstreet%5D=wall%20street&values%5B0%5D=0&values%5B1%5D=1&values%5B2%5D=2