Question

我在将新对象文字添加到数组中时遇到问题。当我使用数组名称时，一切正常。但是，当我切换代码以使用包含数组名称的变量时，它不起作用。

我有6个阵列，如下所示，它们列在我的页面上。单击将保存单击的数组名称保存到名为whichList的变量中。

以下是三个阵列：

student0 = [
  {
    status: "completed",
    goal: "go to store",
    duedate: "November 1",
    datecreated: ""
  }, {
    status: "completed",
    goal: "buy beer",
    duedate: "November 2",
    datecreated: ""
  }
];

student1 = [
  {
    status: "completed",
    goal: "go to the beach",
    duedate: "November 7"
  }, {
    status: "completed",
    goal: "swim without drowning",
    duedate: "November 8",
    datecreated: ""
  }
];

student2 = [
  {
    status: "completed",
    goal: "fly a plane",
    duedate: "November 11",
    datecreated: ""
  }, {
    status: "completed",
    goal: "don't crash",
    duedate: "November 12",
    datecreated: ""
  }
];

这是工作代码，它直接指定数组名称。它在点击后显示我在控制台中更新的数组：

$('#savegoal').click(function() {
  datecreated = new Date();
  student0[student0.length] = {
    status: "pending",
    goal: "\"" + $('#thegoal').val() + "\"",
    duedate: "\"" + $('#thedeadline').val() + "\"",
    datecreated: "\"" + datecreated + "\""
  };
  return console.log(student0);
});

这是非工作代码。我想使用whichList变量。

我已经使用console.log来检查变量是否在函数开头显示正确的数组名称。一切都很好。但是我在控制台中得到的只是数组变量，而不是我在工作版本中所做的数组内容。

$('#savegoal').click(function() {
  datecreated = new Date();
  whichList[whichList.length] = {
    status: "pending",
    goal: "\"" + $('#thegoal').val() + "\"",
    duedate: "\"" + $('#thedeadline').val() + "\"",
    datecreated: "\"" + datecreated + "\""
  };
  return console.log(whichList);
});

Answer 1

您可以使用window[whichList]，因为数组变量可能位于全局/窗口范围内：

var whichList = "student0";
var theList = window[whichList];
theList[theList.length] = { ... };   // consider using instead: theList.push( { ... })

Answer 2

直接回答您的问题：

var wichList = null;
$('#savegoal').click(function() {
  if (wichList == null){
      alert('No list selected');
  }
  // don't forget the "var", otherwise "datecreated"
  // will actually be a global variable
  var datecreated = new Date();
  // ".push()" adds the given value at the end of the array
  wichList.push({
    status: "pending",
    goal: "\"" + $('#thegoal').val() + "\"",
    duedate: "\"" + $('#thedeadline').val() + "\"",
    datecreated: "\"" + datecreated + "\""
  });
  return console.log(wichList);
});

//somewhere else in your code :
if (somecond) {
    wichList = student0;
} elseif (somecond) {
    wichList = student1;
} else {
    wichList = null;
}

以上代码有效：在javascript中，array变量实际上是数组内容的引用

var a = [];
var b = a;
// b an a are now references to the same array,
// any modification to a will be "seen" by b, and vice versa :
a.push(1);
b.push(2);
// a == b == [1,2]

但是，考虑到“学生”变量的名称，这些列表可能应存储在数组中：

var students = [];

students[0] = [{
    status: "completed",
    goal: "go to store",
    duedate: "November 1",
    datecreated: ""
  }, {
    status: "completed",
    goal: "buy beer",
    duedate: "November 2",
    datecreated: ""
  }];

students[1] = [ ...

现在，您可以使用此数组中的索引作为识别学生的方法，可能需要额外选择：

<select id="student">
    <option value="0">student 0</option>
    <option value="1">student 1</option>
    ...
</select>

并在click回调中使用它：

$('#savegoal').click(function() {
  var datecreated = new Date();
  var i = $('#student').val();
  students[i].push({
    status: "pending",
    goal: "\"" + $('#thegoal').val() + "\"",
    duedate: "\"" + $('#thedeadline').val() + "\"",
    datecreated: "\"" + datecreated + "\""
  });
  return console.log(students[i]);
});

Answer 3

首先，使用数组而不是单独的变量：

var student = [
    [{
        status: "completed",
        goal: "go to store",
        duedate: "November 1",
        datecreated: ""
    }, {
        status: "completed",
        goal: "buy beer",
        duedate: "November 2",
        datecreated: ""
    }],
    [{
        status: "completed",
        goal: "go to the beach",
        duedate: "November 7"
    }, {
        status: "completed",
        goal: "swim without drowning",
        duedate: "November 8",
        datecreated: ""
    }],
    [{
        status: "completed",
        goal: "fly a plane",
        duedate: "November 11",
        datecreated: ""
    }, {
        status: "completed",
        goal: "don't crash",
        duedate: "November 12",
        datecreated: ""
    }],
    ...
];

然后，whichList应该是数组的索引（即0到5之间的数字）而不是变量的名称，你可以这样做：

$('#savegoal').click(function() {
    datecreated = new Date().toString();
    student[whichList].push({
        status: "pending",
        goal: $('#thegoal').val(),
        duedate: $('#thedeadline').val(),
        datecreated: datecreated
    });
});

您不需要连接所有这些"\"" - 在键入字符串文字时，引号是符号的一部分，您不需要它们从变量或表达式获取字符串。

如果您想使用学生ID作为寻找每个学生的关键，您可以采取以下措施：

var student = {};
student[student0] = [
    {
        status: "completed",
        goal: "go to store",
        duedate: "November 1",
        datecreated: ""
    }, {
        status: "completed",
        goal: "buy beer",
        duedate: "November 2",
        datecreated: ""
    }];
student[student1] = [
    {
        status: "completed",
        goal: "go to the beach",
        duedate: "November 7"
    }, {
        status: "completed",
        goal: "swim without drowning",
        duedate: "November 8",
        datecreated: ""
    }];
student[student2] = [
    {
        status: "completed",
        goal: "fly a plane",
        duedate: "November 11",
        datecreated: ""
    }, {
        status: "completed",
        goal: "don't crash",
        duedate: "November 12",
        datecreated: ""
    }];

$('#savegoal').click(function() {
    datecreated = new Date();
    push(student[whichStudentId],{
        status: "pending",
        goal: $('#thegoal').val(),
        duedate: $('#thedeadline').val(),
        datecreated: datecreated
    });
    console.log(whichList);
});

如何使用包含数组名称的变量将对象文字添加到数组

3 个答案: