如何使用 JavaScript 从数组数组创建一个简单数组？答案

【问题标题】：How do I create a simple array from an array of array with JavaScript?如何使用 JavaScript 从数组数组创建一个简单数组？
【发布时间】：2013-05-13 09:15:59
【问题描述】：

我想从这样的多维数组创建一个数组：

var dataItaly = [
/*Town       Region   City*/
  ["Castelspina","Piemonte","Alessandria"  ],
  ["Cavatore","Piemonte","Alessandria"  ],
  ["Cella Monte","Piemonte","Alessandria"  ],
  ["Cereseto","Piemonte","Alessandria"  ],
  ["Cantarana","Piemonte","Asti"  ],
  ["Capriglio","Piemonte","Asti"  ],
  ["Casorzo","Piemonte","Asti"  ],
  ["Albino","Lombardia","Bergamo"  ],
  ["Algua","Lombardia","Bergamo"  ],
  ["Abbiategrasso","Lombardia","Milano"  ],
  ["Agrate Brianza","Lombardia","Milano"  ],
  ["Aicurzio","Lombardia","Milano"  ],
  ["Almese","Piemonte","Torino"  ],
  ["Alpette","Piemonte","Torino"  ],
  ["Alpignano","Piemonte","Torino"  ],
  ["Andezeno","Piemonte","Torino"  ],
  ["Albonese","Lombardia","Pavia"  ],
  ["Albuzzano","Lombardia","Pavia"  ],
  ["Arena Po","Lombardia","Pavia"  ],
  ["Badia Pavese","Lombardia","Pavia"  ]
];

这是我的出发点...

var region = "Piemonte"
// array must appear the city of "Piemonte"

function createArrayCity (dataItaly, region) {
var arrayList;
for (i = 0; i <dataItaly.length i) {
  if the region === [1] {
    arrayList [2]. append;
return arrayList;
}
}
}

这个的内容必须是arrayList [Alessandria, Torino, Asti]。如果 var region = "Lombardia" 则 arrayList 的内容为 [Bergamo, Milano, Pavia]

【问题讨论】：

大家非常感谢您的帮助。对我来说，数组中的迭代仍然是一个难题。现在我有了学习的基地

标签： javascript arrays filter

【解决方案1】：

我会使用.map() 和.filter()：

var result = dataItaly.map(function(e) {
    return e[1] === region ? e[2] : null;
}).filter(function(e, i, a) {
    return e !== null && a.indexOf(e) === i;
});

注意：这些方法比较新，一些旧浏览器可能不支持它们。您应该使用垫片（来自here 和here）来修复兼容性。

【讨论】：

【解决方案2】：

你可以使用 concat 来合并数组：

var dataItaly = [
  ["Castelspina","Piemonte","Alessandria"  ],
  ["Cavatore","Piemonte","Alessandria"  ],
  ["Cella Monte","Piemonte","Alessandria"  ],
  ["Arena Po","Lombardia","Pavia"  ],
  ["Badia Pavese","Lombardia","Pavia"  ]
];
var merged = [];
merged = merged.concat.apply(merged, dataItaly);

要删除重复项（如果需要），您可以这样做：

merged = merged.filter (function (v, i, a) { return a.indexOf (v) == i });

【讨论】：

【解决方案3】：

试试

function createArrayCity (dataItaly, region) {
    var arrayList = [];
    for (i = 0; i <dataItaly.length; i++) {
        if (dataItaly[i][1] === region && indexOf(arrayList, dataItaly[i][2]) == -1) {
            arrayList.push(dataItaly[i][2])
        }
    }
    return arrayList;
}

function indexOf(array, obj){
    if(typeof array.indexOf == 'function'){
        return array.indexOf(obj);
    }
    for (i = 0; i <array.length; i++) {
        if(array[i] == obj){
            return i;
        }
    }
    return -1;
}


console.log(createArrayCity(dataItaly, 'Lombardia'))

演示：Fiddle

【讨论】：