在JavaScript中，我创建了一个这样的对象:
var data = {
'PropertyA': 1,
'PropertyB': 2,
'PropertyC': 3
};
如果直到运行时才确定属性名称，那么是否可以在初始创建该对象后向其添加更多属性?即。
var propName = 'Property' + someUserInput
//imagine someUserInput was 'Z', how can I now add a 'PropertyZ' property to
//my object?
当前回答
使用.(点)方法向现有对象添加属性时要小心。
(.dot)方法添加属性到对象应该只使用如果你事先知道'键'否则使用[括号]方法。
例子:
var data = { 'Property1': 1 }; // Two methods of adding a new property [ key (Property4), value (4) ] to the // existing object (data) data['Property2'] = 2; // bracket method data.Property3 = 3; // dot method console.log(data); // { Property1: 1, Property2: 2, Property3: 3 } // But if 'key' of a property is unknown and will be found / calculated // dynamically then use only [bracket] method not a dot method var key; for(var i = 4; i < 6; ++i) { key = 'Property' + i; // Key - dynamically calculated data[key] = i; // CORRECT !!!! } console.log(data); // { Property1: 1, Property2: 2, Property3: 3, Property4: 4, Property5: 5 } for(var i = 6; i < 2000; ++i) { key = 'Property' + i; // Key - dynamically calculated data.key = i; // WRONG !!!!! } console.log(data); // { Property1: 1, Property2: 2, Property3: 3, // Property4: 4, Property5: 5, key: 1999 }
注意控制台日志末尾的问题- 'key: 1999'而不是Property6: 6, Property7: 7，........., Property1999: 1999。因此，添加动态创建的属性的最佳方法是[括号]方法。
其他回答
下面是我解决这个问题的方法。
var obj = {
};
var field = "someouter.someinner.someValue";
var value = 123;
function _addField( obj, field, value )
{
// split the field into tokens
var tokens = field.split( '.' );
// if there's more than one token, this field is an object
if( tokens.length > 1 )
{
var subObj = tokens[0];
// define the object
if( obj[ subObj ] !== undefined ) obj[ subObj ] = {};
// call addfield again on the embedded object
var firstDot = field.indexOf( '.' );
_addField( obj[ subObj ], field.substr( firstDot + 1 ), value );
}
else
{
// no embedded objects, just field assignment
obj[ field ] = value;
}
}
_addField( obj, field, value );
_addField(obj, 'simpleString', 'string');
console.log( JSON.stringify( obj, null, 2 ) );
生成以下对象:
{
"someouter": {
"someinner": {
"someValue": 123
}
},
"simpleString": "string"
}
Yes.
Var数据= { “PropertyA”:1、 “PropertyB”:2 “PropertyC”:3 }; data["PropertyD"] = 4; //对话框中包含4 警报(data.PropertyD); 警报(数据(“PropertyD”));
ES6引入了计算属性名，它允许你这样做
let a = 'key'
let myObj = {[a]: 10};
// output will be {key:10}
是的，这是可能的。我已经实现了使用下面的实现。对于这个，我得到了一个数组作为响应，我想在对象中作为属性列表。
response = {
"equityMonths": [
{
"id": 1,
"month": "JANUARY",
"isEligible": false
},
{
"id": 2,
"month": "FEBRUARY",
"isEligible": true
},
{
"id": 3,
"month": "MARCH",
"isEligible": false
},
{
"id": 4,
"month": "APRIL",
"isEligible": true
},
{
"id": 5,
"month": "MAY",
"isEligible": false
},
{
"id": 6,
"month": "JUNE",
"isEligible": true
},
{
"id": 7,
"month": "JULY",
"isEligible": true
},
{
"id": 8,
"month": "AUGUST",
"isEligible": false
},
{
"id": 9,
"month": "SEPTEMBER",
"isEligible": true
},
{
"id": 10,
"month": "OCTOBER",
"isEligible": false
},
{
"id": 11,
"month": "NOVEMBER",
"isEligible": true
},
{
"id": 12,
"month": "DECEMBER",
"isEligible": false
}
]
}
在这里，我想要equityMonths作为对象，Jan到Dec是键，isEligible作为值。为此，我们必须使用Object类的defineProperty()方法，该方法允许向对象中添加动态属性。
向对象动态添加属性的代码。
let equityMonth = new Object();
response.equityMonths.forEach(element => {
Object.defineProperty(equityMonth, element['month'], {
value: element['isEligible'],
writable: true,
enumerable: true,
configurable: true
});
});
console.log("DATA : " + JSON.stringify(equityMonth));
在上面的代码中，我们有一个equityMonths数组，我们已经将其转换为对象的属性。
输出:
DATA : {"JANUARY":false,"FEBRUARY":true,"MARCH":false,"APRIL":true,"MAY":false,"JUNE":true,"JULY":true,"AUGUST":false,"SEPTEMBER":true,"OCTOBER":false,"NOVEMBER":true,"DECEMBER":false}
如果在运行时添加混合的新属性，它会很有用:
data = { ...data, newPropery: value}
然而，展开运算符使用浅复制，但这里我们将数据赋给自身，因此不会丢失任何数据
