如何在列表中附加字典？答案

【问题标题】：How do I append dictionaries on an list?如何在列表中附加字典？
【发布时间】：2020-01-28 20:23:24
【问题描述】：

我正在尝试创建一个将值存储在字典中的 for 循环，并且每次迭代都会将此字典附加到列表中。

已经尝试使用 push() 和索引列表进行附加，但没有成功。

json = {
    "MUNICIPIOS":[
        {"ATRIBUTOS":["atrib1","atrib2","atrib3"],"VALORES": [10, 100, 1000]},
        {"ATRIBUTOS":["atrib1","atrib2","atrib3"],"VALORES": [20, 200, 2000]},
        {"ATRIBUTOS":["atrib1","atrib2","atrib3"],"VALORES": [30, 300, 3000]},
        {"ATRIBUTOS":["atrib1","atrib2","atrib3"],"VALORES": [40, 400, 4000]}
    ]
};

var atributos = json["MUNICIPIOS"][0]["ATRIBUTOS"];
var municipios = json["MUNICIPIOS"];
var dimensoes = [];
var dicionario = {label:"", values:[]};


for (var atr = 0; atr < atributos.length; atr++){

    dicionario.label = atributos[atr];

    valores = [];
    for (var mun=0; mun < municipios.length; mun++){
        valores.push(municipios[mun]["VALORES"][atr]);
        dicionario.values = valores;
    }

    //dimensoes.push(dicionario);
    dimensoes[atr] = dicionario;
}

console.log(dimensoes);

结果并不如我所愿：

// Actual result
[
  { label: 'atrib3', values: [ 1000, 2000, 3000, 4000 ] },
  { label: 'atrib3', values: [ 1000, 2000, 3000, 4000 ] },
  { label: 'atrib3', values: [ 1000, 2000, 3000, 4000 ] }
]

我需要这个：

// Expected result
[
  { label: 'atrib1', values: [ 10, 20, 30, 40 ] },
  { label: 'atrib2', values: [ 100, 200, 300, 400 ] },
  { label: 'atrib3', values: [ 1000, 2000, 3000, 4000 ] }
]

我做错了什么？

【问题讨论】：

把dicionario = {label:"", values:[]};作为for循环的第一行

标签： javascript dictionary for-loop

【解决方案1】：

您的代码的问题在于您“填充”dicionario 的位置 - 此对象用于所有输出并对其进行修改dimensoes[atr]

var dicionario = {label:"", values:[]};

for (var atr = 0; atr < atributos.length; atr++){

    dicionario.label = atributos[atr];
    // snip - rest of your code
    dimensoes[atr] = dicionario;
}

一种解决方案是更改代码，以便每次迭代都有一个新的dicionario 对象可以使用

var dicionario = {label:"", values:[]};

for (var atr = 0; atr < atributos.length; atr++){

    dicionario = {label:atributos[atr], values:[]};

    //dicionario.label = atributos[atr]; not required as it is set above
    // snip - rest of your code

    dimensoes[atr] = dicionario;
}

但是，对于一个整洁的 ES6+ 解决方案：

const json = {
    "MUNICIPIOS":[
        {"ATRIBUTOS":["atrib1","atrib2","atrib3"],"VALORES": [10, 100, 1000]},
        {"ATRIBUTOS":["atrib1","atrib2","atrib3"],"VALORES": [20, 200, 2000]},
        {"ATRIBUTOS":["atrib1","atrib2","atrib3"],"VALORES": [30, 300, 3000]},
        {"ATRIBUTOS":["atrib1","atrib2","atrib3"],"VALORES": [40, 400, 4000]}
    ]
};

const atributos = json.MUNICIPIOS[0].ATRIBUTOS;
const municipios = json.MUNICIPIOS;
const dimensoes = atributos.map((label, atr) => ({
  label,
  values: municipios.map(municipio => municipio.VALORES[atr])
}));
console.log(JSON.stringify(dimensoes, null, 4));

【讨论】：