添加多個屬性的對象只顯示最後創建的道具

Question

我想2個屬性添加到根據某些條件的對象： 例如：

var data= [ 
       { name:"Jan", score:4, scale:4 }, 
       { name:"Feb",score:8, scale:3 }, 
       { name: "Mar", score:2, scale:9 }, 
       { name: "Apr", score:10, scale:1 } 
] 


data.map(function(point) {  
    if (some condition) { 
    point.m = { 
    a: 2 
    } 
}else { 
    point.m = { 
    a: 10 
    } 
} 
}) 
//so result in the data im expecting to add the prop `m` of type object to the array. 

data = [ 
        { name:"Jan", score:4, scale:4,m:{a:2} }, 
        { name:"Feb",score:8, scale:3,m:{a:2} }, 
        { name: "Mar", score:2, scale:9,m:{a:10} }, 
        { name: "Apr", score:10, scale:1,m:{a:2} } 
    ] 

現在不同的比例我想補充另一場來支撐m，即時通訊做：

point.m = { 
b: 10 // this value is dynamic so could change. 
} 

，所以我很期待：

data = [ 
         { name:"Jan", score:4, scale:4,m:{a:2, b:10} }, 
         { name:"Feb",score:8, scale:3,m:{a:2, b:10} }, 
         { name: "Mar", score:2, scale:9,m:{a:10, b:10} }, 
         { name: "Apr", score:10, scale:1,m:{a:2, b:10} } 
     ] 

但由於某些原因，只需將最後一個字段添加到道具中。我得到的結果如下：

data = [ 
          { name:"Jan", score:4, scale:4,m:{ b:10} }, 
          { name:"Feb",score:8, scale:3,m:{ b:10} }, 
          { name: "Mar", score:2, scale:9,m:{ b:10} }, 
          { name: "Apr", score:10, scale:1,m:{b:10} } 
      ] 

我在這裏錯過了什麼？

Answer 1

你的榜樣的這一部分：

point.m = { 
b: 10 // this value is dynamic so could change. 
} 

是一個新的對象替換point.m。你想合併它，而不是Object.assign。

Object.assign(point.m, { b: 10 }) 

或者，你可以簡單地分配給b直接m

point.m.b = 10 

Answer 2

您重新寫入屬性。

data.map(function(point) { 
    point.m = {};  
    if (some condition) { 
    point.m.a = 2; 
    } else { 
    point.m.a = 10; 
    } 
    } 

    if (some_other_condition) { 
    point.m.b = 10; 
    } 
});