Javascript数组去重

1、ES6 Set

const arr = [1, 2, 1, 2, 3 ,4, 5]

const unique = (arr) => {
  return Array.from(new Set(arr))  // return [...new Set(arr)]
}

unique(arr)

2、利用indexOf、includes

const arr = [1, 2, 1, 2, 3 ,4, 5]

const unique = (arr) => {
  let result = []
  for (let i of arr) {
  	if (result.indexOf(i) === -1) {  // if (!result.includes(i))
    	result.push(i)
    }
  }
  return result
}

unique(arr)

3、for 循环嵌套

const arr = [1, 2, 1, 2, 3 ,4, 5]

const unique = (arr) => {
  for (let i = 0, len = arr.length; i < len; i++) {
  	for(let j = i + 1, len = arr.length; j < len; j++) {
      if(arr[i] === arr[j]) {
      	arr.splice(i, 1)
        j--
      }
    }
  }
  return arr
}

unique(arr)
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4、filter + indexOf

const arr = [1, 2, 1, 2, 3 ,4, 5]

const unique = (arr) => {
  return arr.filter((item, index) => arr.indexOf(item) === index)
}

unique(arr)

5、reduce + includes

const arr = [1, 2, 1, 2, 3 ,4, 5]

const unique = (arr) => {
  return arr.reduce((prev, curr) => prev.includes(curr) ? prev : [...prev, curr], [])
}

unique(arr)

6、sort

const arr = [1, 2, 1, 2, 3 ,4, 5]

const unique = (arr) => {
  arr = arr.sort()
  let result = [arr[0]]
  for (let i = 1, len = arr.length; i < len; i++) {
  	if (arr[i] !== arr[i-1]) {
      result.push(arr[i])
    }
  }
  return result
}

unique(arr)