如何使用javascript訪問位於對象數組中的對象的屬性？

Question

以下是來自ajax調用的responseText的一個元素：

[{
    "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"
    }]
}]

我將字符串轉換為javascript對象：

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

我正在嘗試從此元素（位於元素的末尾）訪問對象數組的屬性，但未成功。 我嘗試了以下操作，但未成功：

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

請您能指教嗎？

Answer 1

首先：修復您的JSON，結尾缺少一個]。 除此之外，您可能還想遍歷所有可能的名字。 嘗試這個：

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

獲取arrayOfPersons的最后一個人：

  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

如果xmlhttp.responseText的返回值類型為json，則無需解析它。 您可以這樣使用：

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