Lodash查找对象属性是否存在于数组中

Question

我有一个这样的对象数组：

[ {"name": "apple", "id": "apple_0"}, 
  {"name": "dog",   "id": "dog_1"}, 
  {"name": "cat", "id": "cat_2"}
]

我想插入另一个名为apple元素，但是，因为我不想在那里重复，我怎样才能使用lodash来查看数组中是否有一个具有相同名称的对象？

Answer 1

你可以像这样使用Lodash _.find() 。

 var data = [ {"name": "apple", "id": "apple_0"}, {"name": "dog", "id": "dog_1"}, {"name": "cat", "id": "cat_2"} ] if(!_.find(data, {name: 'apple'})) { data.push({name: 'apple2'}); } console.log(data) 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.15.0/lodash.min.js"></script> 

参考文档： https ： //lodash.com/docs/4.17.14#find

Answer 2

这是表格

_.has(object, path)

例：

const countries = { country: { name: 'Venezuela' } }
const isExist = _.has(countries, 'country.name')
// isExist = true

有关更多信息，请参阅Lodash文档

Answer 3

这是lodash的另一个例子

var a = [ {"name": "apple", "id": "apple_0"}, 
  {"name": "dog",   "id": "dog_1"}, 
  {"name": "cat", "id": "cat_2"}
]

var b = _.find(a, ['name', "apple2"]);

if(_.isObject(b)){
  console.log('exists')
}else{
    console.log('insert new')
}

https://jsfiddle.net/jorge182/s4og07jg/

Answer 4

您可以使用Array.prototype.find()或lodash的_.find() ：

 const addItem = (arr, item) => { if(!arr.find((x) => x.name === item.name)) { // you can also change `name` to `id` arr.push(item); } }; const arr = [ {"name": "apple", "id": "apple_0"}, {"name": "dog", "id": "dog_1"}, {"name": "cat", "id": "cat_2"} ]; addItem(arr, { "name": "apple", "id": "apple_0" }); addItem(arr, { "name": "pear", "id": "pear_3" }); console.log(arr); 

而且更短但可读性更低：

  const addItem = (arr, item) => arr.find((x) => x.name === item.name) || arr.push(item); // you can also change `name` to `id` const arr = [ {"name": "apple", "id": "apple_0"}, {"name": "dog", "id": "dog_1"}, {"name": "cat", "id": "cat_2"} ]; addItem(arr, { "name": "apple", "id": "apple_0" }); addItem(arr, { "name": "pear", "id": "pear_3" }); console.log(arr); 

Answer 5

这对我有用（在测试出不同的解决方案后）：

  addItem(items, item) {
    let foundObject = _.find(items, function(e) {
      return e.value === item.value;
    });

    if(!foundObject) {
      items.push(item);
    }
    return items;
  }

Answer 6

以下是使用lodash 4.17.5实现此目的的三种方法：

说你要添加对象entry到对象的数组numbers ，只有entry不存在。

let numbers = [
    { to: 1, from: 2 },
    { to: 3, from: 4 },
    { to: 5, from: 6 },
    { to: 7, from: 8 },
    { to: 1, from: 2 } // intentionally added duplicate
];

let entry = { to: 1, from: 2 };

/* 
 * 1. This will return the *index of the first* element that matches:
 */
_.findIndex(numbers, (o) => { return _.isMatch(o, entry) });
// output: 0


/* 
 * 2. This will return the entry that matches. Even if the entry exists
 *    multiple time, it is only returned once.
 */
_.find(numbers, (o) => { return _.isMatch(o, entry) });
// output: {to: 1, from: 2}


/* 
 * 3. This will return an array of objects containing all the matches.
 *    If an entry exists multiple times, if is returned multiple times.
 */
_.filter(numbers, _.matches(entry));
// output: [{to: 1, from: 2}, {to: 1, from: 2}]


/* 
 * 4. This will return `true` if the entry exists, false otherwise.
 */
_.some(numbers, entry);
// output: true

如果要返回一个Boolean （即，假设您没有使用_.some() ），在第一种情况下，您只需检查正在返回的索引值：

_.findIndex(numbers, (o) => { return _.isMatch(o, entry) }) > -1;
// output: true

Lodash文档是示例和实验的重要来源。

Answer 7

如果您只想在数组中插入一个值，那么使用_.find可能是一个选项。 但是，如果您有兴趣插入一个或多个，我建议使用_.unionBy ：

 var currentArr = [{ "name": "apple", "id": "apple_0" }, { "name": "dog", "id": "dog_1" }, { "name": "cat", "id": "cat_2" }], arrayOneValue = [{ "name": "apple", "id": "apple_0" }], arrayTwoValues = arrayOneValue.concat({ "name": "lemon", "id": "lemon_0" }) console.log(_.unionBy(currentArr, arrayOneValue, 'name')); console.log(_.unionBy(currentArr, arrayTwoValues, 'name')); // It also allow you to perform the union using more than one property console.log(_.unionBy(currentArr, arrayTwoValues, 'name', 'id')); 

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