如何使用javascript访问位于对象数组中的对象的属性？

Question

The following is ONE ELEMENT of a responseText from an ajax call:

[{
    "hitcount": {
        "0": "3351"
    },
    "page": {
        "0": "1"
    },
    "title": {
        "0": "Hypoxia upregulates Rab11-family interacting protein 4 through HIF-1\u03b1 to promote the metastasis of hepatocellular carcinoma."
    },
    "authorString": {
        "0": "Hu F, Deng X, Yang X, Jin H, Gu D, Lv X, Wang C, Zhang Y, Huo X, Shen Q, Luo Q, Zhao F, Ge T, Zhao F, Chu W, Shu H, Yao M, Fan J, Qin W."
    },
    "pubYear": {
        "0": "2015"
    },
    "journalVolume": "",
    "issue": "",
    "pageInfo": "",
    "pmid": {
        "0": "25745995"
    },
    "abstract_": {
        "0": "Hypoxic microenvironment is a powerful driving force for the invasion and metastasis of hepatocellular carcinoma (HCC). Hypoxia-inducible factor 1\u03b1 (HIF-1\u03b1), as a crucial regulator of transcriptional responses to hypoxia, induces the expression of multiple target genes involved in different steps of HCC metastatic process. It is critical to find target genes associated with metastasis under hypoxia for shedding new light on molecular mechanism of HCC metastasis. In this study, we uncovered that hypoxia could induce the upregulation of Rab11-family interacting protein 4 (Rab11-FIP4) and activation of Rab11-FIP4 promoter by HIF-1\u03b1. The overexpression of Rab11-FIP4 significantly enhanced the mobility and invasiveness of HCC cells in vitro, also contributed to distant lung metastasis in vivo, whereas silencing of Rab11-FIP4 decreased the ability of migration and invasion in HCC cells in vitro and suppressed lung metastasis in vivo. Rab11-FIP4 facilitated HCC metastasis through the phosphorylation of PRAS40, which was regulated by mTOR. Furthermore, the expression level of Rab11-FIP4 was significantly increased in HCC tissues and high expression of Rab11-FIP4 was closely correlated with vascular invasion and poor prognosis in HCC patients. A markedly positive correlation between the expression of Rab11-FIP4 and HIF-1\u03b1 was observed in HCC tissues and combination of Rab11-FIP4 and HIF-1\u03b1 was a more valuable predictor of poor prognosis for HCC patients. In conclusion, Rab11-FIP4 is a target gene of HIF-1\u03b1 and has a pro-metastatic role in HCC, suggesting that Rab11-FIP4 may be a promising candidate target for HCC treatment.Oncogene advance online publication, 9 March 2015; doi:10.1038\/onc.2015.49."
    },
    "journalTitle": {
        "0": "Oncogene"
    },
    "pdfURL": "",
    "arrayOfPersons": [{
        "firstname": "dean",
        "lastname": "wood",
        "avatar_path": null,
        "username": "deanwood"
    }, {
        "firstname": "dean",
        "lastname": "wood",
        "avatar_path": null,
        "username": "deanwood"
    }, {
        "firstname": "Anne",
        "lastname": "Smith",
        "avatar_path": null,
        "username": "annesmith"
    }]
}]

I convert the string to a javascript object:

 var json_obj = JSON.parse(xmlhttp.responseText);

I am trying to access the properties of the array of objects from this element (located at the end of the element) but have not been successful. I have tried the following without success:

 json_obj[i].arrayOfPersons[i].firstname;

Please can somone advise?

Answer 1

First of all: fix you JSON, it's missing an ] at the end. Other than that you probably want to iterate through all possible firstNames. Try this:

for (var i = 0; i < json_obj.length; i++) {
    for (var j = 0; j < json_obj[i].arrayOfPersons.length; j++) {
        var result = json_obj[i].arrayOfPersons[j];
        console.log(result.firstname);
    }
}

Answer 2

Get the last person of arrayOfPersons :

  var json = '[{"hitcount":{"0":"3351"},"page":{"0":"1"},"title":{"0":"Hypoxia upregulates Rab11-family interacting protein 4 through HIF-1\α to promote the metastasis of hepatocellular carcinoma."},"authorString":{"0":"Hu F, Deng X, Yang X, Jin H, Gu D, Lv X, Wang C, Zhang Y, Huo X, Shen Q, Luo Q, Zhao F, Ge T, Zhao F, Chu W, Shu H, Yao M, Fan J, Qin W."},"pubYear":{"0":"2015"},"journalVolume":"","issue":"","pageInfo":"","pmid":{"0":"25745995"},"abstract_":{"0":"Hypoxic microenvironment is a powerful driving force for the invasion and metastasis of hepatocellular carcinoma (HCC). Hypoxia-inducible factor 1\α (HIF-1\α), as a crucial regulator of transcriptional responses to hypoxia, induces the expression of multiple target genes involved in different steps of HCC metastatic process. It is critical to find target genes associated with metastasis under hypoxia for shedding new light on molecular mechanism of HCC metastasis. In this study, we uncovered that hypoxia could induce the upregulation of Rab11-family interacting protein 4 (Rab11-FIP4) and activation of Rab11-FIP4 promoter by HIF-1\α. The overexpression of Rab11-FIP4 significantly enhanced the mobility and invasiveness of HCC cells in vitro, also contributed to distant lung metastasis in vivo, whereas silencing of Rab11-FIP4 decreased the ability of migration and invasion in HCC cells in vitro and suppressed lung metastasis in vivo. Rab11-FIP4 facilitated HCC metastasis through the phosphorylation of PRAS40, which was regulated by mTOR. Furthermore, the expression level of Rab11-FIP4 was significantly increased in HCC tissues and high expression of Rab11-FIP4 was closely correlated with vascular invasion and poor prognosis in HCC patients. A markedly positive correlation between the expression of Rab11-FIP4 and HIF-1\α was observed in HCC tissues and combination of Rab11-FIP4 and HIF-1\α was a more valuable predictor of poor prognosis for HCC patients. In conclusion, Rab11-FIP4 is a target gene of HIF-1\α and has a pro-metastatic role in HCC, suggesting that Rab11-FIP4 may be a promising candidate target for HCC treatment.Oncogene advance online publication, 9 March 2015; doi:10.1038\\/onc.2015.49."},"journalTitle":{"0":"Oncogene"},"pdfURL":"","arrayOfPersons":[{"firstname":"dean","lastname":"wood","avatar_path":null,"username":"deanwood"},{"firstname":"dean","lastname":"wood","avatar_path":null,"username":"deanwood"},{"firstname":"Anne","lastname":"Smith","avatar_path":null,"username":"annesmith"}]}]'; function show() { var json_obj = JSON.parse(json); result = document.getElementById("result"); lastPerson = json_obj[0].arrayOfPersons[json_obj[0].arrayOfPersons.length - 1]; result.innerHTML = lastPerson.firstname + " " +lastPerson.lastname; } 

 Last person of arrayOfPersons: <div id="result"></div> <button onclick="show();">Show</button> 

Answer 3

if the type of return value of xmlhttp.responseText is json you doesn't need to parse it. You can use like this:

var json_obj = xmlhttp.responseText;
json_obj[i].arrayOfPersons[i].firstname