Add objectToQueryString utility function and it's unit tests

snippets/objectToQueryString.md

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+---
+title: objectToQueryString
+tags: utility,object,function,intermediate
+---
+
+Generates a query string from key values pairs from given object.
+
+Attaches `?` in front of query string and ignores any non-string
+values and their corresponding keys from given object. The function
+returns empty string as a result if there is no single valid
+key-value pair in given object, else returns generated query string.
+
+```js
+const objectToQueryString = (queryParameters) => {
+  return queryParameters
+    ? Object.entries(queryParameters).reduce((queryString, [key, val], index) => {
+        const symbol = index === 0 ? '?' : '&';
+        queryString += (typeof val === "string") ? `${symbol}${key}=${val}` : '';
+        return queryString;
+      }, '')
+    : '';
+};
+```
+
+```js
+objectToQueryString({page: '1', size: "2kg", key: undefined}); // '?page=1&size=2kg'
+```

test/objectToQueryString.test.js

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+const {objectToQueryString} = require('./_30s.js');
+
+test('objectToQueryString is a Function', () => {
+  expect(objectToQueryString).toBeInstanceOf(Function);
+});
+
+test("{page: '1', size: '2kg', key: '21'} to give '?page=1&size=2kg&key=21'", () => {
+  expect(
+    objectToQueryString({page: '1', size: '2kg', key: '21'})
+  ).toEqual('?page=1&size=2kg&key=21');
+});
+
+test("{page: '1', size: '2kg', key: undefined} to give '?page=1&size=2kg'", () => {
+  expect(
+    objectToQueryString({page: '1', size: '2kg', key: undefined})
+  ).toEqual('?page=1&size=2kg');
+});
+
+test("{} to give ''", () => {
+  expect(
+    objectToQueryString({})
+  ).toEqual('');
+});
+
+test("{page: 1, size: null, key: undefined} to give ''", () => {
+  expect(
+    objectToQueryString({page: 1, size: null, key: undefined})
+  ).toEqual('');
+});