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洛达斯_。仅当对象存在时设置

lodash javascript

klugjo · 技术社区 · 7 年前

我希望仅当对象的内部属性已经存在时才设置它们。洛达斯 _.set 如果不存在,将创建整个层次结构。

有没有简单的方法?(没有和如果声明?)

下面的代码段:

const obj = {a: {b: 1}};

_.set(obj, 'a.b', 2);

console.log(obj); // Great !

_.set(obj, 'a.c', 1);

console.log(obj); // Great but not what I want. I would like c not to be set because it does not exist in the first place

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

4 回复 | 直到 7 年前

Kalaiselvan 7 年前

你可以这样试试

const obj = {a: {b: 1}};

_.set(obj, 'a.b', 2);

console.log(obj); // Great !
_.has(obj,'a.c')==true?_.set(obj, 'a.c', 1):""

console.log(obj); // Great but not what I want. I would like c not to be set because it does not exist in the first place

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

Jaromanda X 7 年前

你可以看看 Object.seal

不过,您需要“深度”密封该对象:

const sealDeep = obj => {
    const sealProps = o => {
        Object.values(o).forEach(value => {
            if (typeof value === 'object') {
                sealProps(value);
                Object.seal(value);
            }
        });
    };
    sealProps(obj);
    Object.seal(obj);
};

var x = {
    hello: {
        world: {
            foo: 1,
            bar: 2
        },
        bat: '3'
    },
    foo2: 4
};
sealDeep(x);
console.log(JSON.stringify(x));
x.newthing = 999;
x.hello.newthing = 999;
x.hello.world.newthing = 999;
x.hello.world.foo = 999;
console.log(JSON.stringify(x));

klugjo 7 年前

下面来自Kalaiselvan A的答案让我走上了正轨,但这并不是我想要的。

使用相同的想法,但改进了三元结构,得到了以下我满意的解决方案。

const obj = {a: {b: 1}};

_.has(obj, 'a.b') && _.set(obj, 'a.b', 2);

console.log(obj);

_.has(obj, 'a.c') && _.set(obj, 'a.c', 2);

console.log(obj);

<script src="https://cdn.jsdelivr.net/lodash/4/lodash.min.js"></script>

sscarduzio 3 年前

我也在寻找同样的东西,并满足于这种非lodash解决方案

function overridePropertyByJsonPath(obj, thePath, value) {
  const path = thePath.split('.');
  let i
  for (i = 0; i < path.length - 1; i++) {
    const val = obj[path[i]]
    if (val === undefined) {
      return
    }
    obj = val
  }
  if (obj[path[i]] === undefined) {
    return
  }
  obj[path[i]] = value;
}

它通过了我提出的所有测试


describe("Key overriding should allow ", () => {
  it("override shallow key", () => {
    const o = { a1: true }
    overridePropertyByJsonPath(o, "a1", false)
    expect(o["a1"]).toEqual(false)
  })
  it("no extra key with non-empty object", () => {
    const o = { a1: true }
    overridePropertyByJsonPath(o, "a2", false)
    expect(o["a2"]).toBeUndefined()
  })

  it("no extra keys with empty object", () => {
    const o = {}
    overridePropertyByJsonPath(o, "not_there_to_begin_with", true)
    expect(o["not_there_to_begin_with"]).toBeUndefined()
  })
  it("no extra keys in override (deep)", () => {
    const o = { a: { b: true } }
    overridePropertyByJsonPath(o, "a.b.not_there_to_begin_with", true)
    expect(o["a"]["b"]["not_there_to_begin_with"]).toBeUndefined()
  })
  it("no extra keys in override (too deep)", () => {
    const o = { a: { b: true } }
    overridePropertyByJsonPath(o, "a.b.c.not_there_to_begin_with", true)
    expect(o["a"]["b"]["c"]).toBeUndefined()
  })
  it("override deep key", () => {
    const o = { a: { b: true } }
    overridePropertyByJsonPath(o, "a.b", false)
    expect(o["a"]["b"]).toEqual(false)
  })
  it("override deep key with array value", () => {
    const o = { a: { b: [1] } }
    overridePropertyByJsonPath(o, "a.b", [2])
    expect(o["a"]["b"]).toContain(2)
    expect(o["a"]["b"].length).toEqual(1)
  })
  it("override deep key with object value", () => {
    const o = { a: { b: {} } }
    overridePropertyByJsonPath(o, "a.b", { "x": true })
    expect(o["a"]["b"]["x"]).toEqual(true)
  })

})