Undefined when trying to use the received valid JSON

Question

I’m having a hard time finding the error, I’ve been looking here for hours. I am receiving a PHP JSON using Jquery, I can visualize it as can see below the result of the answer "date":

{
    "sucesso": 1,
    "dados": {
        "BTC_YAMRUB": {
            "result": 500000,
            "url_redirect": "https:\/\/mysite.com\/?rid=1229109",
            "https": 1,
            "link_permanente": "mysite",
            "nome": "MySite",
            "exchange_rates": 500000,
            "idade": "3 anos e 1 m\u00eas",
            "wmid": null,
            "pais_nome": "Brasil",
            "moeda_from": "Bitcoin BTC",
            "moeda_to": "Yandex money RUB",
            "rank_from": "14",
            "rank_to": "38",
            "reviews": [{
                "cliente_site": "52",
                "positivo": "0",
                "comentario": "0",
                "negativo": "0"
            }],
            "offer": {
                "from": 0,
                "to": 0,
                "in": 1,
                "out": 500000,
                "amount": 121436.1859,
                "minfee": 0,
                "fromfee": 0,
                "tofee": 0,
                "minamount": 0,
                "param": "manual"
            }
        }
     }
}

but while trying any of the lines below I get undefined.

console.log(data[0].length);
console.log(data.length);
console.log(data.dados.length);

The javascript code:

function getRates()
{
    $("#gif_load").show();

    $.post(URL_SITE + '/api/exchangers', {from: $("#from").val(), to: $("#to").val()}, function(data, textStatus, xhr) {

        if(textStatus == "success") {

            $("#exchangers tbody tr").remove();

            console.log(data.length); // undefined
            console.log(Object.keys(data).length); // 2

            if(data.dados.length > 0)
            {
                  $.each(data.dados, function(index, el) {
                      console.log(el.result);
                  });
            }
          }

     });

}

The code of PHP:

<?php
ini_set('display_errors', 1);
include_once(dirname(__FILE__)."/../includes/_conect.php");

$limit_blocktraill = 300;

header('Content-Type: application/json');
$url_invalid  = URL_SITE . '/';
$url_valid = str_replace(":80", "", $url_invalid);

if(!empty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest' && strpos($_SERVER["HTTP_REFERER"], $url_valid) !== false)
{
    if(isset($_POST["from"]) && isset($_POST["to"]))
    {
        $from = mysqli_real_escape_string($_POST["from"]);
        $to = mysqli_real_escape_string($_POST["to"]);

        #--------------------MemCached-----------------------------------------
        $memCached = new Memcached();
        $memCached->addServer('localhost', 11211);

        if ($dados = $memCached->get('rank_moeda')) {
            if ($memCached->getResultCode() == Memcached::RES_NOTFOUND) {
                $exchangers = 0;
            }else{
                $exchangers = $dados;
            }
        }

        if(count($exchangers) > 0)
        {
            echo json_encode(array("sucesso" => 1, "dados" => $exchangers));

        }else{
            echo json_encode(array("sucesso1" => 1, "dados" => array()));
        }

    }else{
        echo json_encode(array("sucesso2" => 0, "Erro" => "Error"));
    }

}else{
    echo json_encode(array("sucesso3" => 0, "Erro" => "Error"));
}

I checked the whole answer on https:/jsonlint.com/ and it’s OK. To some other test I can do to find out what’s going on?

Answer 1

It turns out that Javascript does not return the size of the object, only of arrays. That’s why you’re making the mistake Undefined.

Remembering that every time you return (observe the brackets in the example below):

{
    "sucesso": 1,
    "dados": [{
        ...
    }]
}

Javascript will interpret as a JSON Array and automatically add the property length.

And every time you return:

{
    "sucesso": 1,
    "dados": {
        ...
    }
}

Javascript will interpret as a JSON Object and nay will add the property length

But there is a way to go through an object. Just return all the keys of the object and then execute a for..of.

Example:

$.post('SUA-URL', {}, function(data, textStatus, xhr) {

    if(textStatus == "success") {

        $("#exchangers tbody tr").remove();

        /* Captura as keys */
        let keys = Object.keys(data.dados);

        /* Exibe a quantidade */
        console.log( keys.length );

        /* Verifica se há keys */
        if ( keys ) {

            /* Percorre os valores através da key */
            for (let d of keys) {
                console.log( data.dados[d]);
            }
        }
      }

 });

Or you can return all values with Object.values.

Example:

$.post('SUA-URL', {}, function(data, textStatus, xhr) {

    if(textStatus == "success") {

        $("#exchangers tbody tr").remove();

        /* Captura todos os valores */
        let values = Object.values(data.dados);

        /* Exibe a quantidade de valores */
        console.log( values.length );

        /* Verifica se há valores disponíveis */
        if ( values ) {

            /* Percorre todos os valores */
            for (let v of values) {
                console.log( v );
            }
        }
      }

 });

Answer 2

Look, the data should be counted like this:

Object.keys(data).length // retorna 2

Dice:

Object.keys(data.dados).length // retorna 1

For simplicity you can do it like this:

var tmp = Object.keys(data);
console.log(tmp.length);
console.log(tmp.dados.length);