Question

我试过谷歌搜索这个问题并搜索了stackoverflow，但没有成功，所以作为最后的手段，我要求以防万一有人能指出我正确的方向。

我举了一个例子，说明我的代码如下所示。

var objectInfo = [
{
    name:"object1",
    materials: [{
        name: "wood",
        quantity:10
    }, {
        name: "stone",
        quantity:16
    }],
}, {
    name:"object2",
    materials: [{
        name: "wood",
        quantity:10
    }, {
        name: "stone",
        quantity:16
    }, {
        name: "bricks",
        quantity:100
    }],
}]

我的问题是，如何获得材质对象数组的长度？

我实现这一目标的尝试如下：

function getMaterialsArrayLength(objName) {
    for (i = 0; i < objectInfo.length; i++) {
        if (objectInfo[i].name == objName) {
            return objectInfo[i].materials.length
        }
    }    
};

但是返回的错误是“无法读取未定义的属性材料”。有没有人有找到阵列长度的潜在解决方案？

如果之前已发布过，我道歉。

Answer 1

＆＃13;

var objectInfo = [{
  name: "object1",
  materials: [{
    name: "wood",
    quantity: 10
  }, {
    name: "stone",
    quantity: 16
  }],
}, {
  name: "object2",
  materials: [{
    name: "wood",
    quantity: 10
  }, {
    name: "stone",
    quantity: 16
  }, {
    name: "bricks",
    quantity: 100
  }],
}]

function getMaterialsLength(objName) {
  return objectInfo.find(o => o.name === objName).materials.length;
}

console.log(getMaterialsLength('object2'));

＆＃13;

可能想要添加一些错误检查。

Answer 2

您无法获得不存在的数组的长度;更确切地说，您所查看的数组的元素是未定义的，因此没有找到长度的材料：

Answer 3

只需通过索引访问对象：

＆＃13;

var objectInfo = [
{
    name:"object1",
    materials: [{
        name: "wood",
        quantity:10
    }, {
        name: "stone",
        quantity:16
    }],
}, {
    name:"object2",
    materials: [{
        name: "wood",
        quantity:10
    }, {
        name: "stone",
        quantity:16
    }, {
        name: "bricks",
        quantity:100
    }],
}];

console.log("objectInfo[0].materials.length: " + objectInfo[0].materials.length);
console.log("objectInfo[1].materials.length: " + objectInfo[1].materials.length);

＆＃13;

Answer 4

使用lodash.js。

var objectInfo = [
{
    name:"object1",
    materials: [{
        name: "wood",
        quantity:10
    }, {
        name: "stone",
        quantity:16
    }],
}, {
    name:"object2",
    materials: [{
        name: "wood",
        quantity:10
    }, {
        name: "stone",
        quantity:16
    }, {
        name: "bricks",
        quantity:100
    }],
}];
function getMaterialsLength(objName) {
  _.each(objectInfo, function(obj) {
      if (obj.name == objName) {  
        console.log(_.size(obj.materials));
      }
  });
}
getMaterialsLength('object2');

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/1.2.1/lodash.min.js"></script>

如何在javascript中获取对象数组中对象数组的长度？

4 个答案: