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"}
]
我想插入另一个元素，也命名为apple，但是，因为我不想在其中重复，我如何使用 lodash 来查看数组中是否已经存在同名的对象？
【问题讨论】：
ARRAY.find(function(el){ return el.name === 'apple'; }) 如果undefined，则数组中没有名称为"apple"的元素
_.has(object, path)
标签： javascript arrays reactjs lodash
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>【讨论】：
这是表格
_.has(object, path)
例子：
const countries = { country: { name: 'Venezuela' } }
const isExist = _.has(countries, 'country.name')
// isExist = true
欲了解更多信息Document Lodash
【讨论】：
你可以使用Array.prototype.find()或者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);还有一个更短但可读性较差的版本：
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);【讨论】：
[0,1,2] 的数组并且您正在查找0，在这种情况下为!0 === true;，在这种特定情况下，您的方法很好:)
这是另一个使用 lodash 的例子
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')
}
【讨论】：
这对我有用（在测试了不同的解决方案之后）：
addItem(items, item) {
let foundObject = _.find(items, function(e) {
return e.value === item.value;
});
if(!foundObject) {
items.push(item);
}
return items;
}
【讨论】：
如果您只想在数组中插入一个值，则可以选择使用_.find。但是，如果您有兴趣插入一个或多个，我建议您改用_.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'));<script src="https://cdn.jsdelivr.net/lodash/4.16.4/lodash.min.js"></script>【讨论】：
以下是使用lodash 4.17.5 实现此目的的三种方法：
假设您想将对象entry 添加到对象数组numbers 中，前提是entry 尚不存在。
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
如果你想返回一个Boolean（即假设你没有使用_.some()），在第一种情况下，你可以简单地检查返回的索引值：
_.findIndex(numbers, (o) => { return _.isMatch(o, entry) }) > -1;
// output: true
Lodash documentation 是示例和实验的重要来源。
【讨论】：