javascript - 如何根据 obj 标志的状态查找数组长度

Question

我有一系列待办事项，我试图显示已完成的未完成待办事项的数量。我知道我可以执行 array.length 并且可以找到总数量，但在这种情况下我是堆栈。

this.state = {
  text: '',
  notes: [
     {todo: "hello", completed: true},
     {todo: "world", completed: false}
  ]
}

全部(notes.length) 2 已完成(?) 0 未完成(?) 0

Answer 1

使用过滤器

let completedCount = this.state.notes.filter(n => n.completed).length;
let incompleteCount = this.state.notes.length - completedCount;

或使用减少

let result = this.state.notes.reduce( (acc, curr) => {
   if(curr.completed) acc.complete++;
   else acc.incomplete++;
   return acc;
}, {complete:0,incomplete:0});
console.log(result.complete); // 1
console.log(result.incomplete); // 1