下划线“默认”从头开始

发布于 2025-01-15 21:22:14 字数 548 浏览 4 评论 0原文

我一直在尝试从 underscore.js 重写 _.defaults 方法，但不断收到此错误：

应该将源属性复制到目标对象中未定义的属性‣ AssertionError：预期 { a: 'existing' } 深度等于 { a: 'existing', b: 2, c: 3, d: 4 }

这是缺少的条件：

- 应将源属性复制到目标对象中未定义的属性，并应返回目标对象

和我的代码：

_.defaults = function (destination, source) {
  Object.keys(destination).forEach(key => {
    if (destination[key] === undefined || destination[key] === null) {
      destination[key] = source[key];
    }
  })
  return destination;

};

原文

I've been trying to rewrite the _.defaults method from underscore.js and I keep getting this error:

should copy source properties to undefined properties in the destination object‣
AssertionError: expected { a: 'existing' } to deeply equal { a: 'existing', b: 2, c: 3, d: 4 }

Here's the missing conditions:

-should copy source properties to undefined properties in the destination object and should return the destination object

and my code:

_.defaults = function (destination, source) {
  Object.keys(destination).forEach(key => {
    if (destination[key] === undefined || destination[key] === null) {
      destination[key] = source[key];
    }
  })
  return destination;

};

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何时共饮酒 2025-01-22 21:22:14

_.defaults 中的想法是源对象中的键可能会丢失完全在目标对象中。因此，您需要迭代源对象的键而不是目标对象的键：

_.defaults = function (destination, source) {
  Object.keys(source).forEach(key => {
    if (destination[key] === undefined || destination[key] === null) {
      destination[key] = source[key];
    }
  })
  return destination;

};

附注：您可以编写 x == null 而不是 x === null || x === 未定义。节省一些宝贵的击键次数。

_.defaults = function (destination, source) {
  Object.keys(source).forEach(key => {
    if (destination[key] == null) {
      destination[key] = source[key];
    }
  })
  return destination;

};

The idea in _.defaults is that keys from the source object might be missing entirely in the destination object. So you need to iterate the keys of the source object instead of those of the destination object:

_.defaults = function (destination, source) {
  Object.keys(source).forEach(key => {
    if (destination[key] === undefined || destination[key] === null) {
      destination[key] = source[key];
    }
  })
  return destination;

};

Side note: you can write x == null instead of x === null || x === undefined. Saves some precious keystrokes.

_.defaults = function (destination, source) {
  Object.keys(source).forEach(key => {
    if (destination[key] == null) {
      destination[key] = source[key];
    }
  })
  return destination;

};

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