Flatten a javascript object to pass as querystring

Question

I have a javascript object that I need to flatten into a string so that I can pass as querystring, how would I do that? i.e:

{ cost: 12345, insertBy: \'testUse

Answer 1

ES6 version of Jrop's answer (also parses nested params)

const toQueryString = (obj, urlEncode = false) => {
  if (!obj) return null;
  const flattenObj = (x, path = []) => {
    const result = [];
    Object.keys(x).forEach((key) => {
      if (!Object.prototype.hasOwnProperty.call(x, key)) return;
      const newPath = path.slice();
      newPath.push(key);
      let vals = [];
      if (typeof x[key] === 'object') {
        vals = flattenObj(x[key], newPath);
      } else {
        vals.push({ path: newPath, val: x[key] });
      }
      vals.forEach((v) => {
        return result.push(v);
      });
    });
    return result;
  };

  let parts = flattenObj(obj);
  parts = parts.map((varInfo) => {
    if (varInfo.path.length === 1) {
      varInfo.path = varInfo.path[0]; // eslint-disable-line no-param-reassign
    } else {
      const first = varInfo.path[0];
      const rest = varInfo.path.slice(1);
      varInfo.path = `${first}[${rest.join('][')}]`; // eslint-disable-line no-param-reassign
    }
    return varInfo;
  });

  const queryString = parts.map((varInfo) => {
    return `${varInfo.path}=${varInfo.val}`;
  }).join('&');
  if (urlEncode) {
    return encodeURIComponent(queryString);
  }
  return queryString;
};