Javascript 为对象数组创建新属性时，对象不可扩展错误
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Object is not extensible error when creating new attribute for array of objects
提问by Mendes
I have a function that needs to extend a javascript array, including a new attribute called selected:
我有一个需要扩展 javascript 数组的函数，包括一个名为 的新属性selected：
export const initSelect = (data) => {
let newData = data.concat();
newData.map((item) => {
item.selected = false;
})
return newData;
}
datais a ReactJS state value (comes from this.state.datawhen calling the function), but this didn't seem to be a problem as newDatais a new copy of dataarray...
data是一个 ReactJS 状态值（来自this.state.data调用函数时），但这似乎不是问题，因为newData是data数组的新副本......
I'm getting the following error:
我收到以下错误：
TypeError: Cannot add property selected, object is not extensible
回答by Jonas Wilms
You probably need to copy the objects:
您可能需要复制对象：
export const initSelect = (data) => {
return data.map((item) => ({
...item,
selected: false
}));
}
回答by lilezek
You can not extend itemwith selectedproperty, and your array is just a shallow copy.
你不能item用selected属性扩展，你的数组只是一个浅拷贝。
If you want to be able to extend, you will have to do a deep copy of your array. It may be enough with:
如果您希望能够扩展，则必须对数组进行深度复制。这可能就足够了：
let newData = data.map((item) =>
Object.assign({}, item, {selected:false})
)
回答by Omar
const newObj = Object.assign({selected: false}, data);
const newObj = Object.assign({selected: false}, data);
