这三个点到底是什么意思？我为什么需要它们？
export function leadReducer(state: Lead[]= [], action: Action {
switch(action.type){
case ADD_LEAD:
return [...state, action.payload];
case REMOVE_LEAD:
return state.filter(lead => lead.id !== action.payload.id )
}
}
这三个点被称为来自Typescript 的spread operator(也来自ES7).
扩展运算符返回数组的所有元素.就像您单独编写每个元素一样:
let myArr = [1, 2, 3];
return [1, 2, 3];
//is the same as:
return [...myArr];
这主要是语法上的糖，因为它编译了以下内容:
func(...args);
为此:
func.apply(null, args);
In your case this gets compiled 为此:
return [...state, action.payload];
//gets compiled 为此:
return state.concat([action.payload]);