JavaScript 数组去重的多种方式

const animals = ["Dog", "Cat", "Mouse", "Horse", "Dog", "Rhino"];

1、Set Object

const animalsSet = new Set(animals);

const uniqueAnimals1 = [...animalsSet];
const uniqueAnimals2 = Array.from(animalsSet); 

或一行搞定

const uniqueAnimals = [...new Set(animals)];

2、filter()

const uniqueAnimals = animals.filter(
  (animal, i) => animals.indexOf(animal) === i
)

3、reduce() & includes()

const uniqueAnimals = animals.reduce((result, element) => (
  result.includes(element) ? result : [...result, element]
), [])

4、reduce() & Object.values()

 const uniqueAnimals = Object.values(animals.reduce((pre, cur) => {
    pre[cur] = cur
    return pre
  }, {}))

5、forEach()

const uniqueAnimals = [];

animals.forEach(animal => {
  if (!uniqueAnimals.includes(animal)) {
    uniqueAnimals.push(animal)
  }
});

6、indexOf

const uniqueAnimals = [];
    
for (let i = 0; i < animals.length; i++) {
  if (!~uniqueAnimals.indexOf(animals[i])) {
      uniqueAnimals.push(animals[i])
  }
}

7、将出现过的元素通过键的形式添加到对象中

const has = {};
const uniqueAnimals = [];

for (let i = 0; i < animals.length; i++) {
  if (!has[animals[i]]) {
    has[animals[i]] = true;
    uniqueAnimals.push(animals[i])
  }
}

8、先排序，再判断

animals.sort();   
const uniqueAnimals = [];

for (var i = 0; i < animals.length; i++) { 
  if(animals[i] !== uniqueAnimals[uniqueAnimals.length - 1]){  
    uniqueAnimals.push(animals[i]);  
  }              
}