javascript - 我似乎无法更新 javascript/typescript 中数组中对象字段的值？

Question

这看起来非常简单，但我似乎无法更新数组中 WorkSetTemplate 对象中 pos 字段的值。

代码如下:

export class WorkSetTemplate {

  static alignPositionWithDisplay(coll: WorkSetTemplate[]): WorkSetTemplate[] {
    for (let i = 0; i < coll.length; i++) {
      coll[i].pos = i + 1;
    }
    return coll;
  }

  constructor(
    public id?: number,
    public nk?: string,
    public pos?: number,
    public name?: string,
    public maintainerId?: number,
    public airworthinessDirectiveIssueNumber?: string,
    public workItemTemplates?: WorkItemTemplate[]
  ) {}

}

假设我从集合开始:

我用以下方式调用静态方法:

sets = WorkSetTemplate.alignPositionWithDisplay(sets);

我希望看到相同的对象排列，但 pos 值按顺序读取为 1, 2, 3(而不是 2, 1, 3)

但实际上并没有发生任何变化(即，它们仍然是 2, 1, 3，即使我在 for 循环中 console.log ，变化实际上发生了(在循环中)。所以当你退出循环。我显然在这里遗漏了一些非常基本的东西。有人可以告诉我我误解了什么吗？

Answer 1

这里的场景缺少一些东西，因为项目可能会发生变化(有或没有返回值分配)。

interface WorkItemTemplate {
    name: string;
}

class WorkSetTemplate {

  static alignPositionWithDisplay(coll: WorkSetTemplate[]): WorkSetTemplate[] {
    for (let i = 0; i < coll.length; i++) {
      coll[i].pos = i + 1;
    }
    return coll;
  }

  constructor(
    public id?: number,
    public nk?: string,
    public pos?: number,
    public name?: string,
    public maintainerId?: number,
    public airworthinessDirectiveIssueNumber?: string,
    public workItemTemplates?: WorkItemTemplate[]
  ) {}

}

let items = [
    new WorkSetTemplate(5, 'ABC3', 1),
    new WorkSetTemplate(5, 'XYZ1', 1),
    new WorkSetTemplate(5, 'ABC1', 1),
];

console.log(JSON.stringify(items));

// [
//   { "id": 5, "nk": "ABC3", "pos": 1 },
//   { "id": 5, "nk": "XYZ1", "pos": 1 },
//   { "id": 5, "nk": "ABC1", "pos": 1 }
// ]

// Side note - the objects are changed regardless of assignment
WorkSetTemplate.alignPositionWithDisplay(items);

console.log(JSON.stringify(items));

// [
//   { "id": 5, "nk": "ABC3", "pos": 1 },
//   { "id": 5, "nk": "XYZ1", "pos": 2 },
//   { "id": 5, "nk": "ABC1", "pos": 3 }
// ]

使用转译代码进行演示:

var WorkSetTemplate = /** @class */ (function () {
    function WorkSetTemplate(id, nk, pos, name, maintainerId, airworthinessDirectiveIssueNumber, workItemTemplates) {
        this.id = id;
        this.nk = nk;
        this.pos = pos;
        this.name = name;
        this.maintainerId = maintainerId;
        this.airworthinessDirectiveIssueNumber = airworthinessDirectiveIssueNumber;
        this.workItemTemplates = workItemTemplates;
    }
    WorkSetTemplate.alignPositionWithDisplay = function (coll) {
        for (var i = 0; i < coll.length; i++) {
            coll[i].pos = i + 1;
        }
        return coll;
    };
    return WorkSetTemplate;
}());
var items = [
    new WorkSetTemplate(5, 'ABC3', 1),
    new WorkSetTemplate(5, 'XYZ1', 1),
    new WorkSetTemplate(5, 'ABC1', 1),
];
console.log(JSON.stringify(items));
WorkSetTemplate.alignPositionWithDisplay(items);
console.log(JSON.stringify(items));