filterToQueryString - JavaScript function to turn current filter into a query string

15 March 2018   1 comment   Web development, Javascript, ReactJS

tl;dr; this function:

export const filterToQueryString = (
filterObj, overrides) => {
  const copy = Object.assign(overrides || {}, filterObj)
  const searchParams = new URLSearchParams()
  Object.entries(copy).forEach(([key, value]) => {
    if (Array.isArray(value) && value.length) {
      value.forEach(v => searchParams.append(key, v))
    } else if (value) {
      searchParams.set(key, value)
    }
  })
  searchParams.sort()
  return searchParams.toString()
}

I have a React project that used to use query-string to serialize and deserialize objects between React state and URL query strings. Yesterday version 6.0.0 came out and now I'm getting this error during yarn run build:

yarn run v1.5.1
$ react-scripts build
Creating an optimized production build...
Failed to compile.

Failed to minify the code from this file: 

    ./node_modules/query-string/index.js:8 

Read more here: http://bit.ly/2tRViJ9

error An unexpected error occurred: "Command failed.
Exit code: 1

Perhaps this is the wake up call to switch to URLSearchParams (documentation here). Yes it is. Let's do it.

My use case is that I store a dictionary of filters in React this.state. The filter object is updated by submitting a form that looks like this:

Fitler form

Since the form inputs might be empty strings my filter dictionary in this.state might look like this:

{
  user: '@mozilla.com', 
  created_at: 'yesterday', 
  size: '>= 1m, <300G', 
  uploaded_at: ''
}

What I want that to become is: created_at=yesterday&size=>%3D+1m%2C+<300G&user=%40mozilla.com
So it's important to be able to skip falsy values (empty strings or possibly empty arrays).

Sometimes there are other key-values that needs to be added that isn't part of what the user chose. So it needs to be easy to squeeze in additional key-values. Here's the function:

export const filterToQueryString = (filterObj, overrides) => {
  const copy = Object.assign(overrides || {}, filterObj)
  const searchParams = new URLSearchParams()
  Object.entries(copy).forEach(([key, value]) => {
    if (Array.isArray(value) && value.length) {
      value.forEach(v => searchParams.append(key, v))
    } else if (value) {
      searchParams.set(key, value)
    }
  })
  searchParams.sort()
  return searchParams.toString()
}

I use it like this:

_fetchUploadsNewCountLoop = () => {
  const qs = filterToQueryString(this.state.filter, {
    created_at: '>' + this.state.latestUpload
  })
  const url = '/api/uploads?' + qs
  ...
  fetch(...)
}

UPDATE - May 2018

In the original blog post (now edited and corrected) I copied the wrong code and didn't discover the subtle mistake until now.
What was wrong as the order of the arguments to Object.assign().

Wrong

const copy = Object.assign(filterObj, overrides || {})

Correct

const copy = Object.assign(overrides || {}, filterObj)

The old version was dangerous because it mutated the filterObj passed in. So if you did something like

const qs = filterToQueryString(this.state.filter, {
  created_at: '>' + this.state.latestUpload
})

it would potentially mutate this.state.filter which isn't desirable.

Comments

Anonymous
URLSearchParams has problem with the Internet Explorer

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