在Javascript中将对象属性转换为逗号分隔值

Question

在这里，我想将对象属性转换为逗号分隔值，如下所示 - 将数组的元素连接成一个字符串：

var fruits = {"f1":"Banana", "f2":"Orange", "f3":"Apple","f4":"Mango"};
var energy = Object.keys(fruits).map(function(k){return fruits[k]}).join(",");

能量的结果将是：

Banana,Orange,Apple,Mango

但是当我这样申请时-

 var fruits = {"f1":"Banana", "f2":"null", "f3":"Apple","f4":"Mango"};
 var energy = Object.keys(fruits).map(function(k){return fruits[k]}).join(",");

能量的结果是这样的：

Banana,,Apple,Mango

我想要这样的结果-

Banana,null,Apple,Mango

我已经尝试了这些链接，但没有找到运气。

Easy way to turn properties of Javascript object into comma-separated list?

更新了问题

var fruits = {"f1":"Banana", "f2":"", "f3":"Apple","f4":"Mango"};
var energy = Object.keys(fruits).map(function(k){return fruits[k]}).join(",");

能量的结果是这样的：

Banana,,Apple,Mango

我想要这样的结果-

 Banana,null,Apple,Mango

Answer 1

使用Object.values 会更容易。

// for "null"
var fruits = {"f1":"Banana", "f2":"null", "f3":"Apple","f4":"Mango"};
var energy = Object.values(fruits).join(",");
console.log(energy);

// for null
var fruits = {"f1":"Banana", "f2":null, "f3":"Apple","f4":"Mango"};
var energy = Object.values(fruits).map(String).join(",");
console.log(energy);

// for ""
var fruits = {"f1":"Banana", "f2":"", "f3":"Apple","f4":"Mango"};
var energy = Object.values(fruits).map(v=>v===""?"null":String(v)).join(",");
console.log(energy);

Answer 2

var fruits = {"f1":"Banana", "f2":"", "f3":"Apple","f4":"Mango"};
var energy = Object.keys(fruits).map(function(k){
    if(fruits [k] ==="") return "null";
    return fruits [k]        
    }).join(",");

Answer 3

关于join()，不显示值null作为字符串"null"，您可以在map()中查看，如下：

var fruits = {"f1":"Banana", "f2":"", "f3":"Apple","f4":"Mango"};
        var energy = Object.keys(fruits)
        .map(function(k){
        return (fruits[k] === "" || fruits[k] === null) ? "null" : fruits [k];
        })
        .join(",");
        console.log(energy);