Question

嗨，我的项目中有以下代码。问题是最后一个项目被推入数组而不是每个项目。

JS函数

function getArrayObjForKeys(keys, source, desiredKeys) {
  let arrayObj = [],
    obj = {};
  source.forEach(function(val, ind) {
    keys.forEach(function(v, i) {
      (function(v) {
        if (val.hasOwnProperty(v)) {
          let desKey = desiredKeys[i];
          obj[desKey] = val[v];
        }
      }).call(this, v);
    });
    arrayObj.push(obj);
  });
  return arrayObj;
}

// Invoking function as below
// **************************

var source = [{
  'country': 'USA',
  'descr': 'United States'
}, {
  'country': 'UK',
  'descr': 'United Kingdom'
}];
var countryList = getArrayObjForKeys(['country', 'descr'], source, ['value', 'label']);
console.info(countryList);

所需的输出

[{'value':'USA','label':'United States'},{'value':'UK','label':'United Kingdom'}]

柱塞

https://next.plnkr.co/edit/3SKbaJo9r5QX8hex?open=lib%2Fscript.js

Answer 1

您的问题是您要在内存中引用相同的obj，从而修改两个对象。对此的快速解决方案是将对象声明移到foreach循环中，因此您对每个对象都有自己的唯一引用（不相同）。

请参见下面的工作示例：

function getArrayObjForKeys(keys, source, desiredKeys) {
  let arrayObj = []
  
  source.forEach(function(val, ind) {
    let obj = {}; /* Move into foreach */
    keys.forEach(function(v, i) {
      (function(v) {
        if (val.hasOwnProperty(v)) {
          let desKey = desiredKeys[i];
          obj[desKey] = val[v];
        }
      }).call(this, v);
    });
    arrayObj.push(obj);
  });
  return arrayObj;
}


var source = [{
  'country': 'USA',
  'descr': 'United States'
}, {
  'country': 'UK',
  'descr': 'United Kingdom'
}];

var countryList = getArrayObjForKeys(['country', 'descr'], source, ['value', 'label']);
console.info(countryList);

Answer 2

您可以使用reduce将源映射到所需的输出，以将键，desirableKeys和对象减少到新对象：

function getArrayObjForKeys(keys, source, desiredKeys) {
    return source.map(function(obj) {
        return keys.reduce(function(result, key, index) {
            result[desiredKeys[index]] = obj[key];
            return result;
        }, {});
    });
}

var source = [{ country: 'USA', descr: 'United States' }, { country: 'UK', descr: 'United Kingdom' }];
var countryList = getArrayObjForKeys(['country', 'descr'], source, ['value', 'label']);
console.info(countryList);

Answer 3

这是使用reduce，Object.entries和map的另一种方法：

function getArrayObjForKeys(keys, source, desiredKeys) {
  return source.map(obj => Object.entries(obj).reduce((accum, [key, val]) => {
    const keyIdx = keys.indexOf(key);
    accum[desiredKeys[keyIdx]] = val;
    return accum;
  }, {}));
}

const source = [
  { 'country': 'USA', 'descr': 'United States' },
  { 'country': 'UK', 'descr': 'United Kingdom' }
];

const countryList = getArrayObjForKeys(['country', 'descr'], source, ['value', 'label']);

console.info(countryList);

Answer 4

使用ES6（并且两个输入数组始终具有相同的长度）的更简洁的选择是：

const getArrayObjForKeys = (keys, source, desiredKeys) => source.map( obj => {
	let output = {};
	keys.forEach( (key,i) => output[desiredKeys[i]] = obj[keys[i]]);
	return output;
})
 

const source = [{'country':'USA','descr':'United States'},{'country':'UK','descr':'United Kingdom'}],
	  countryList = getArrayObjForKeys(['country','descr'], source, ['value','label']);

console.info(countryList);

Answer 5

getArrayObjForKeys(keys,source,desiredKeys){
    let arrayObj=[];
    source.forEach(function(val,ind){
    let obj={};
        keys.forEach(function(v,i){
          (function(v){
            if(val.hasOwnProperty(v)){
              let desKey = desiredKeys[i];
              obj[desKey] = val[v];
            }
          }).call(this, v);
        });
        arrayObj.push(obj);
    });
    return arrayObj;
  }

在foreach循环中更新obj变量。

问题与obj变量

Answer 6

如果您想要更少的代码，这是一个更具体的功能。

function easy(obj) {
  return obj = obj.map(obj => {
    return {"value": obj.country, "lable": obj.descr};
  });
}

obj = [{
  "country": "USA",
  "descr": "United States"
}, {
  "country": "UK",
  "descr": "United Kingdom"
}];

obj = easy(obj);

console.log(obj);

最后一项被推送到数组（Javascript）

6 个答案: