How to correctly use axios params with arrays

How to add indexes to array in query string?

I tried send data like this:

axios.get('/myController/myAction', { params: { storeIds: [1,2,3] })

And I got this url:

http://localhost/api/myController/myAction?storeIds[]=1&storeIds[]=2&storeIds[]=3

So, I should to get this url:

http://localhost/api/myController/myAction?storeIds[0]=1&storeIds[1]=2&storeIds[2]=3

What I should add in my params options to get this url?

You can use paramsSerializer and serialize parameters with https://www.npmjs.com/package/qs

axios.get('/myController/myAction', {
  params: {
    storeIds: [1,2,3]
  },
  paramsSerializer: params => {
    return qs.stringify(params)
  }
})

Without having to add more libraries and using ES6 you could write:

axios.get(`/myController/myAction?${[1,2,3].map((n, index) => `storeIds[${index}]=${n}`).join('&')}`);

Thanks so much the answer from Nicu Criste, for my case, the API requires params like this:

params: {
  f: {
    key: 'abc',
    categories: ['a','b','c']
   },
  per_page: 10
}

Method is GET and this API requires the format is: API?f[key]=abc&f[categories][]=a&f[categories][]=b... So I assigned the paramsSerializer of axios like this:

config.paramsSerializer = p => {
      return qs.stringify(p, {arrayFormat: 'brackets'})
    }

• Install qs please go to this link
  

• Read more about paramsSerializer in axios document

• Edit format of params: Read more at qs stringifying document

In my case, I use ES6 array function. array element make querystring use reduce function. Object array also works.

const storeIds = [1,2,3]
axios.get('some url', {
  params: {
    storeIds: storeIds.reduce((f, s) => `${f},${s}`)
  }
})

In my case, I am using someting like this

const params = array.map((v)=>{
            return `p=${v}&`
        })

Only concat params.join('') to the URL where you get data:

`url_to_get?${params.join('')`

In my back-end in ASP.net I receive this

[FromUri] string [] p

I rewrote the existing paramSerializer shipped in axios. The following snippet does the same serialization while putting indices between square brackets. I tried qs but it is not compatible with my python connexion backend (for JSON string parameters).

const rcg = axios.create({
    baseURL: `${url}/api`,
    paramsSerializer: params => {
        const parts = [];

        const encode = val => {
            return encodeURIComponent(val).replace(/%3A/gi, ':')
                .replace(/%24/g, '$')
                .replace(/%2C/gi, ',')
                .replace(/%20/g, '+')
                .replace(/%5B/gi, '[')
                .replace(/%5D/gi, ']');
        }

        const convertPart = (key, val) => {
            if (val instanceof Date)
                val = val.toISOString()
            else if (val instanceof Object)
                val = JSON.stringify(val)

            parts.push(encode(key) + '=' + encode(val));
        }

        Object.entries(params).forEach(([key, val]) => {
            if (val === null || typeof val === 'undefined')
                return

            if (Array.isArray(val))
                val.forEach((v, i) => convertPart(`${key}[${i}]`, v))
            else
                convertPart(key, val)
        })

        return parts.join('&')
    }
});

I got using "paramSerializer" a bit confuse. Before looking for the "right way" to use axios with array querystring on Google, I did following and got working:

var options = {};
var params = {};
for(var x=0;x<Products.length;x++){
   params[`VariableName[${x}]`] = Products[x].Id;
}
options.params = params;

axios.get(`https://someUrl/`, options)...

It is going to create querystring parameters like:

VariableName[0]=XPTO,VariableName[1]=XPTO2

which the most webservers expected as array format

I know that this approach is not very good and I don't know the downsides it may have, but i tried this and it worked:

before making the request, prepare the params:

  let params = '?';

  for (let i = 0; i < YOUR_ARRAY.length; i++) {  // In this case YOUR_ARRAY == [1, 2, 3]
    params += `storeIds=${YOUR_ARRAY[i]}`;  // storeIds is your PARAM_NAME
    if (i !== YOUR_ARRAY.length - 1) params += '&';
  }

And then make the request like so:

axios.get('/myController/myAction' + params)

This answer is inspired by @Nicu Criste's answer.

But might be not related to the posted question.

The following code was used to generate the query params with repetitive keys which had been supplied with an object array.

Note: If you are a developer with bundlephobia, use the following approach with care: as with UrlSearchParams support varies on different browsers and platforms.

const queryParams = [{key1: "value1"}, {key2: "value2"}]

axios.get('/myController/myAction', {
  params: queryParams,
  paramsSerializer: params => {
    return params.map((keyValuePair) => new URLSearchParams(keyValuePair)).join("&")
  }
})

// request -> /myController/myAction?key1=value1&key2=value2

This work it for me:

axios.get("/financeiro/listar",{
        params: {
          periodo: this.filtro.periodo + "",
          mostrarApagados: this.filtro.mostrarApagados,
          mostrarPagos: this.filtro.mostrarPagos,
          categoria: this.filtro.categoria,
          conta: this.filtro.conta
        }
      })

This was better for me:

axios.get('/myController/myAction', {
params: { storeIds: [1,2,3] + ''}

})

In my case, there was already jQuery implemented into my codebase. So I just used the predefined method.

jQuery.param(Object)