Question

我有以下JSON对象数组：

"employees":[
    {"firstName":"John", "lastName":"Doe"}, 
    {"firstName":"Anna", "lastName":"Smith"}, 
    {"firstName":"Peter","lastName":"Jones"}
]

我想获得JSON数组中的特定键：

for (var ke in employees) {
       if (employees.hasOwnProperty(ke)) {
             console.log(employees[ke].lastName);
       };

但它不起作用!!

Answer 1

你在for循环结束时错过了一个结束的大括号，它应该是：

for (var ke in employees) {
   if (employees.hasOwnProperty(ke)) {
         console.log(employees[ke].lastName);
   };
}

Demo

但是，您可以使用angular.forEach代替，如下所示：

angular.forEach(employees, function (ke) {
    if(ke.lastName) {
        console.log(ke.lastName);
    }
});

Demo

Answer 2

遍历Javascript数组时，请使用标准for循环而不是for...in。

for (var i=0; i < employees.length; i+=1) {
    console.log(employees[i].lastname);
}

或者，ES5现在提供了一个Array.forEach功能，也可以使用。

employees.forEach( function (employee) { 
  console.log(employee.lastname);
}

Answer 3

试试这个

for (var index in employees) {
    var tp = employees[index];
    console.log(tp['yourkeyhere']);
}

Answer 4

方法：1 - 更多验证。

var employees= [
    {"firstName":"John", "lastName":"Doe"}, 
    {"firstName":"Anna", "lastName":"Smith"}, 
    {"firstName":"Peter","lastName":"Jones"}
];

for(var obj in employees) {
    if(employees.hasOwnProperty(obj)){
        for(var prop in employees[obj]){
            if(employees[obj].hasOwnProperty(prop)){
                alert(prop + ' : ' + employees[obj][prop]);
                //to change the key's value
                if(employees[obj][prop] == 'Smith'){
                    employees[obj][prop]='Mike';
                } 
            }
        }
    }
}

Plunker

方法：2 未经验证（不推荐）

   for(i in employees) {
       var obj = employees[i];
       for(j in obj) {
           var key = j;
           var val = obj[j];
           alert(key + " : " + val);   
       }
    }

修改

var employees={"firstName":"John", "lastName":"Doe"}; Object.keys(employees); // return ["firstName", "lastName"]

Object有一个prototype keys，在Array
中返回keys Object个Object.keys
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Answer 5

将您的代码更改为以下内容。它工作正常。

employees=[
        {"firstName":"John", "lastName":"Doe"}, 
        {"firstName":"Anna", "lastName":"Smith"}, 
        {"firstName":"Peter","lastName":"Jones"}
    ]
    for(var ke in employees) {
           if (employees.hasOwnProperty(ke)) {
                 console.log(employees[ke].lastName);
           };
   }

angular如何在json数组中显示键

5 个答案: