在 class 方法中从数组中删除元素

Question

I was working on a hackerrank problem and test cases showed that something was wrong with my 'remove' method. I always got undefined instead of true/false.

I know splice returns array of deleted elements from an array. When I console.log inside map, it looked like everything was fine when I was deleting first element (I was getting what I expected except true/false). But when 'name' I am deleting is not first element, I didn't get what I expected to get. Could you help me fix this? And of course, I never get true or false...

 class StaffList { constructor() { this.members = []; } add(name, age) { if (age > 20) { this.members.push(name) } else { throw new Error("Staff member age must be greater than 20") } } remove(name) { this.members.map((item, index) => { if(this.members.includes(name)) { console.log(name) let removed = this.members.splice(item, 1); console.log(removed) return true; } else { return false; } }) } getSize() { return this.members.length; } } let i = new StaffList; i.add('michelle', 25) i.add('john', 30); i.add('michael', 30); i.add('jane', 26); i.remove('john'); console.log(i);

Answer 1

Your return statements are wrapped within .map() (which you misuse in this particular case, so you, essentially, build the array of true / false ), but your remove method does not return anything.

Instead, I would suggest something, like that:

remove(name){
   const matchIdx = this.members.indexOf(name)
   if(matchIdx === -1){
     return false
   } else {
     this.members.splice(matchIdx, 1)
     return true
   }
}

Answer 2

In the remove method, you're using map with the array, which runs the function you give as argument for each array element. But I believe you don't want to do that.

Using the example you have bellow, basically what you do there is check if the array contains the name 'john' , and if so, you delete the first item that appears in the array (which would be 'michelle' ). This happens because the map function will run for every element, starting on the first one, and then you use that item to be removed from the array. After that, it returns the function, and no other elements get removed.

So my suggestion is just getting rid of the map function and running its callback code directly in the remove method (you would need to get the name's index in the array to use the splice method).

Answer 3

It is not clear why you need to use iterative logic to remove an item. You can simply use findIndex() to get the position of the member in the array. If the index is not -1 , then you can use Array.prototype.slice(index, 1) to remove it. See proof-of-concept example below:

 class StaffList { constructor() { this.members = []; } add(name, age) { if (age > 20) { this.members.push(name) } else { throw new Error("Staff member age must be greater than 20") } } remove(name) { const index = this.members.findIndex(x => x === name); if (index.== -1) { this.members,splice(index; 1). } } getSize() { return this.members;length; } } let i = new StaffList. i,add('michelle'. 25) i,add('john'; 30). i,add('michael'; 30). i,add('jane'; 26). i;remove('john'). console;log(i);

Answer 4

Use a filter method instead of map it's more elegant and you can return the rest of the array as well instead of true or false unless the problem you're working on requires true of false specifically. You could write something like this:

remove(name) {
   if (!this.members.some(el => el === name)) return false;
   this.members = this.members.filter(item => item !== name);
   return true;
}