如何检查值是否未定义以便不将其添加为对象字段？

Question

我正在开发一个 Angular 应用程序，我对使用 TypeScript 有以下疑问，如果值未定义，如何正确避免将字段插入对象。

在我的代码中，我以这种方式创建了一个对象：

let aestheticEvaluation: AestheticEvaluation = {
    "altezza": aestheticEvaluationInfo.get('altezza').value,
    "peso": aestheticEvaluationInfo.get('peso').value,
    "phototype": aestheticEvaluationInfo.get('phototype').value.name,
    "photoaging": aestheticEvaluationInfo.get('photoaging').value.name,
    "comedoni": aestheticEvaluationInfo.get('comedoni').value.name,
    "varici": aestheticEvaluationInfo.get('varici').value.name,
    "rugheGlifiche": aestheticEvaluationInfo.get('rugheGlifiche').value.name,
    "accentuazioneDeiPigheNasogeniene": aestheticEvaluationInfo.get('accentuazioneDeiPigheNasogeniene').value.name,
    "gradoAgingCollo": aestheticEvaluationInfo.get('gradoAgingCollo').value.name,
    "occhiaie": aestheticEvaluationInfo.get('occhiaie').value.name,
    "borse": aestheticEvaluationInfo.get('borse').value.name,
    "ipotoniaTerzoInferiore": aestheticEvaluationInfo.get('ipotoniaTerzoInferiore').value.name,
    "cellulite": aestheticEvaluationInfo.get('cellulite').value.name,
    "cicatriciIpertroficheCheloidi": aestheticEvaluationInfo.get('cicatriciIpertroficheCheloidi').value,
    "luceDiWood": aestheticEvaluationInfo.get('luceDiWood').value,
    "notes": aestheticEvaluationInfo.get('notes').value,
};

问题是某些字段可能具有 undefined 值。在这种情况下，该字段不必插入到我的 aestheticEvaluation 对象中。

例如，如果 aestheticEvaluationInfo.get('altezza').value 值为 undefined，则此 "altezza" 字段不是插入对象

我知道我可以使用 if 语句来检查每个字段的值是否为 null 并且在这种情况下避免插入对象但这样代码会很多更多余。有没有办法直接进入我的对象定义？

Answer 1

创建一个函数，在创建对象之前检查对象中的每个值，如下所示。

// data structure of `aestheticEvaluationInfo` seems to be a map
let aestheticEvaluationInfo = new Map();
aestheticEvaluationInfo.set('altezza', { value: { name: 'altezza'}});
aestheticEvaluationInfo.set('peso', { value: { name: 'peso'}});
.
.
.
// rest of the fields
aestheticEvaluationInfo.set('notes', undefined);


function createObjWithValues(data) {
  let obj = {};
  for (const [key, value] of data.entries()) {
    if (value) obj[key] = value.value.name;
  }
  return obj;
}

console.log(createObjWithValues(aestheticEvaluationInfo));

Answer 2

这是一种与其他解决方案略有不同的方法，但允许您只声明每个条件一次，并快速更改获取值的方法，因为它只在一行上。

let aestheticEvaluationCriteria: string[] = [
  "altezza",
  "peso",
  "phototype",
  "photoaging",
  "comedoni",
  "varici",
  "rugheGlifiche",
  "accentuazioneDeiPigheNasogeniene",
  "gradoAgingCollo",
  "occhiaie",
  "borse",
  "ipotoniaTerzoInferiore",
  "cellulite",
  "cicatriciIpertroficheCheloidi",
  "luceDiWood",
  "notes",
]

let aestheticEvaluation: AestheticEvaluation = {}
aestheticEvaluationCriteria.forEach((criteria)=>{
  const value = aestheticEvaluationInfo.get(criteria).value
  if (value){
    aestheticEvaluation[criteria] = value
  }
})
//aestheticEvaluation is now filled as specified
console.log(aestheticEvaluation)

Answer 3

  let aestheticEvaluation: AestheticEvaluation = {
   "altezza": aestheticEvaluationInfo.get('altezza').value,
   "peso": aestheticEvaluationInfo.get('peso').value,
   ....  so on
  }


  for(let key in aestheticEvaluation)
  { 
   if(!aestheticEvaluation[key]) 
    delete aestheticEvaluation[key]
   }

    !aestheticEvaluation[key] = This will include all falsy values such as 
    null,undefined,0,''.
    If you just want to check for undefined value you can use 
   for(let key in aestheticEvaluation)
    { 
     if(typeof aestheticEvaluation[key] === "undefined") 
      delete aestheticEvaluation[key]
    }

Answer 4

所以我想到了两种解决方案，您可以选择更适合您的一种。

1. 默认值而不是 undefined，在这种情况下，您将值设置为默认值（即空字符串 ''，或数字为零等）。

const object = {
    key: anotherObject?.attribute || ''
};

1. 设置对象值，最后清理对象（删除未定义的值）：

const object = { key: value };

Object.keys( object ).forEach( key => {
    if ( !object[key] ) delete object[key];
} );

如果我有什么误解，请告诉我。