JSON object to query string (using underscore/lodash)

Object2QS.js

var objectToQueryString = function(obj) {
	var qs = _.reduce(obj, function(result, value, key) {
			return (!_.isNull(value) && !_.isUndefined(value)) ? (result += key + '=' + value + '&') : result;
	}, '').slice(0, -1);
	return qs;
};

This ignores object properties that are null/undefined

Thanks for the code. I made some update so that arrays within obj are recognized.

var obj = {
    a: 1,
    b: 2,
    c: [3, 4, 5, null, 7]
};

var objectToQueryString = function (obj) {
    var qs = _.reduce(obj, function (result, value, key) {
        if (!_.isNull(value) && !_.isUndefined(value)) {
            if (_.isArray(value)) {
                result += _.reduce(value, function (result1, value1) {
                    if (!_.isNull(value1) && !_.isUndefined(value1)) {
                        result1 += key + '=' + value1 + '&';
                        return result1
                    } else {
                        return result1;
                    }
                }, '')
            } else {
                result += key + '=' + value + '&';
            }
            return result;
        } else {
            return result
        }
    }, '').slice(0, -1);
    return qs;
};

console.log(objectToQueryString(obj));

https://jsfiddle.net/kr3j0f4a/1/

!_.isNull(value) && !_.isUndefined(value) could be simpler as !_.isNil(value)

Perfect ! @TravelingTechGuy

Using _.forOwn instead of _.reduce (null checks removed):

const obj = {
    a: 1,
    b: 2,
    c: [3, 4, 5, null, 7]
};

const objectToQueryString = obj => {
  const results = [];
  _.forOwn(obj, (value, key) => {
    if (Array.isArray(value)) {
    	_.forOwn(value, value => {
      	results.push(`${key}=${value}`);
      });
    } else {
    	results.push(`${key}=${value}`);
    }
  });
  return results.join('&');
};

console.log(objectToQueryString(obj));

https://jsfiddle.net/ddaanxfr/1/

_.map(obj, (value, key) => `${key}=${value}`).join('&')

Here's some other options that don't require lodash.

'use strict'
// Other ways APIs implement URLSearchParams. Not my own, but I can't find the original source.
// https://developer.mozilla.org/en-US/docs/Web/API/URLSearchParams/URLSearchParams

var obj = {
  a: 1,
  b: 2,
  c: [3, 4, 5, null, 7],
  foo: {bar: 'baz'}
};

function URLSearchParamsWithArrayBrackets(obj, prefix) {
  let str = [],
    p;
  for (p in obj) {
    if (obj.hasOwnProperty(p)) {
      let k = prefix ? prefix + "[]" : p,
        v = obj[p];
      str.push(
        v !== null && typeof v === "object"
          ? URLSearchParamsWithArrayBrackets(v, k)
          : encodeURIComponent(k) + "=" + encodeURIComponent(v)
      );
    }
  }
  return str.join("&");
}

function URLSearchParamsWithArrayIndices(obj, prefix) {
  let str = [],
    p;
  for (p in obj) {
    if (obj.hasOwnProperty(p)) {
      let k = prefix ? prefix + "[" + p + "]" : p,
        v = obj[p];
      str.push(
        v !== null && typeof v === "object"
          ? URLSearchParamsWithArrayIndices(v, k)
          : encodeURIComponent(k) + "=" + encodeURIComponent(v)
      );
    }
  }
  return str.join("&");
}

var params;
params = new URLSearchParams(obj).toString(); // 'a=1&b=2&c=3%2C4%2C5%2C%2C7&foo=%5Bobject+Object%5D'
params = URLSearchParamsWithArrayBrackets(obj); // 'a=1&b=2&c%5B%5D=3&c%5B%5D=4&c%5B%5D=5&c%5B%5D=null&c%5B%5D=7&foo%5B%5D=baz'
params = URLSearchParamsWithArrayIndices(obj); // 'a=1&b=2&c%5B0%5D=3&c%5B1%5D=4&c%5B2%5D=5&c%5B3%5D=null&c%5B4%5D=7&foo%5Bbar%5D=baz'

From https://gist.github.com/3ch01c/37b7a292c744628f189eeabc917a309b/

Object.entries(someobject).reduce((result, item)=>{return result += ${item[0]}=${item[1]}&}, '').slice(0, -1)