如何从对象数组创建数组答案

【问题标题】：How to create an array from an array of objects如何从对象数组创建数组
【发布时间】：2016-09-20 16:45:53
【问题描述】：

鉴于以下情况：

var example = [{
  "logged": {
    "status": 0,
    "status_name": "Logged",
    "hours": 23 // to the hours array
  },
  "pending": {
    "status": 3,
    "status_name": "Pending",
    "contribution": {
      "hours": 0,
      "count": 0
    },
    "verification": {
      "hours": 6, // to the hours array
      "count": 1
    }
  },
  "denied": {
    "status": 4,
    "status_name": "Denied",
    "contribution": {
      "hours": 0,
      "count": 0
    },
    "verification": {
      "hours": 0, // to the hours array
      "count": 0
    }
  },
  "approved": {
    "status": 2,
    "status_name": "Approved",
    "contribution": {
      "hours": 4.5,
      "count": 1
    },
    "verification": {
      "hours": 0, // to the hours array
      "count": 0
    }
  }
}];

我将如何构造两 (2) 个这样的数组：

var statusNames = ["Logged", "Pending", "Denied", "Approved"];
var hours = [23, 6, 0, 0];

如果解决方案中的值，我可以推断出如何获得其余部分。

【问题讨论】：

数组中有更多条目还是只有1个？
那么，你想要一个包含所有键的数组，另一个包含特定键的所有值的数组——一个可以任意嵌套的数组——对吗？
我猜这不是简单的方法，您需要遍历每个元素并将其添加到数组中
只是Array#map 的一个常规用例...您付出了哪些努力？
@PritamBanerjee 我认为这并不难。在我看来，第一个任务是微不足道的，第二个任务很简单。已经有内置方法可以在数组中进行交互以产生这些结果。

标签： javascript arrays arraylist

【解决方案1】：

您可以遍历数组和键，检查属性是否存在并将想要的部分包含到数组中。

var example = [{ "logged": { "status": 0, "status_name": "Logged", "hours": 23 }, "pending": { "status": 3, "status_name": "Pending", "contribution": { "hours": 0, "count": 0 }, "verification": { "hours": 6, "count": 1 } }, "denied": { "status": 4, "status_name": "Denied", "contribution": { "hours": 0, "count": 0 }, "verification": { "hours": 0, "count": 0 } }, "approved": { "status": 2, "status_name": "Approved", "contribution": { "hours": 4.5, "count": 1 }, "verification": { "hours": 0, "count": 0 } } }],
    statusNames = [],
    hours = [];

example.forEach(function (o) {
    Object.keys(o).forEach(function (k) {
        if ('hours' in o[k]) {
            statusNames.push(k);
            hours.push(o[k].hours);
            return;
        }
        if ('verification' in o[k]) {
            statusNames.push(k);
            hours.push(o[k].verification.hours);
        }
    });
});
console.log(statusNames);
console.log(hours);

【讨论】：

【解决方案2】：

使用Object.keys方法获取所有对象属性名数组，然后使用Array#map方法生成结果数组。

// array for storing the hours value
var hours = [];
// genarte the statusName array
var statusNames = Object.keys(example[0]) // get object keys
            // iterate over key value          
            .map(function(k) {
                // get the value of hour and push it to hours array
                // get `hours` property if defined or get hours property
                // of nested object verification or push 0
                hours.push(example[0][k].hours || example[0][k].verification.hours || 0); 
                // get the status name and return
                return example[0][k].status_name;
            })

var example = [{
  "logged": {
    "status": 0,
    "status_name": "Logged",
    "hours": 23 // to the hours array
  },
  "pending": {
    "status": 3,
    "status_name": "Pending",
    "contribution": {
      "hours": 0,
      "count": 0
    },
    "verification": {
      "hours": 6, // to the hours array
      "count": 1
    }
  },
  "denied": {
    "status": 4,
    "status_name": "Denied",
    "contribution": {
      "hours": 0,
      "count": 0
    },
    "verification": {
      "hours": 0, // to the hours array
      "count": 0
    }
  },
  "approved": {
    "status": 2,
    "status_name": "Approved",
    "contribution": {
      "hours": 4.5,
      "count": 1
    },
    "verification": {
      "hours": 0, // to the hours array
      "count": 0
    }
  }
}];

var hours = [];
var statusNames = Object.keys(example[0]).map(function(k) {
  hours.push(example[0][k].hours || example[0][k].verification.hours || 0);
  return example[0][k].status_name;
})

console.log(hours, statusNames)

【讨论】：

【解决方案3】：

你必须使用 Array.prototype.reduce 来过滤你需要的信息。

var example = [{
  "logged": {
    "status": 0,
    "status_name": "Logged",
    "hours": 23 // to the hours array
  },
  "pending": {
    "status": 3,
    "status_name": "Pending",
    "contribution": {
      "hours": 0,
      "count": 0
    },
    "verification": {
      "hours": 6, // to the hours array
      "count": 1
    }
  },
  "denied": {
    "status": 4,
    "status_name": "Denied",
    "contribution": {
      "hours": 0,
      "count": 0
    },
    "verification": {
      "hours": 0, // to the hours array
      "count": 0
    }
  },
  "approved": {
    "status": 2,
    "status_name": "Approved",
    "contribution": {
      "hours": 4.5,
      "count": 1
    },
    "verification": {
      "hours": 0, // to the hours array
      "count": 0
    }
  }
}]

var statusNames = example.reduce(function(prevVal, currVal) {
  for(var key in currVal) {
    if(!Object.prototype.hasOwnProperty.call(currVal, key)) continue

    if(currVal[key].status_name) {
      prevVal.push(currVal[key].status_name)
    }
   
  }
  return prevVal
}, [])


console.log(statusNames)

【讨论】：

【解决方案4】：

这应该可行。

// get all of the objects keys
var statusNames = Object.keys(example);
var hours = [];

// get all of the hours
example.forEach( function(item, idx){
    idx === 0 ? hours.push(item.hours) : false; // because the hours in your first object is not nested.
    idx > 0 ? hours.push(item.verification.hours) : false; // gets all of the nested hours.
});

【讨论】：

【解决方案5】：

使用for (var key in example[0]) 迭代每个键。

然后将值压入各自的数组中

statusNames.push(key); hours.push(example[0][key]["hours"] || example[0][key]["verification"]["hours"] );

var  statusNames = [];
   var hours = [];
   
var example = [{
  "logged": {
    "status": 0,
    "status_name": "Logged",
    "hours": 23 // to the hours array
  },
  "pending": {
    "status": 3,
    "status_name": "Pending",
    "contribution": {
      "hours": 0,
      "count": 0
    },
    "verification": {
      "hours": 6, // to the hours array
      "count": 1
    }
  },
  "denied": {
    "status": 4,
    "status_name": "Denied",
    "contribution": {
      "hours": 0,
      "count": 0
    },
    "verification": {
      "hours": 0, // to the hours array
      "count": 0
    }
  },
  "approved": {
    "status": 2,
    "status_name": "Approved",
    "contribution": {
      "hours": 4.5,
      "count": 1
    },
    "verification": {
      "hours": 0, // to the hours array
      "count": 0
    }
  }
}];


for (var key in example[0]) {
      statusNames.push(key);
			hours.push(example[0][key]["hours"] || example[0][key]["verification"]["hours"] );
     
}
console.log(statusNames);
console.log(hours);

【讨论】：