数组去除重复值的四种超简便方法

方式一：使用filter()

let arr1 = [1, 4, 4, 3, 1, 2, 5, 5, 9, 1]
let arr2 = []
// item:当前项，index:当前索引，arr:当前数组
arr1.filter((item, index, arr) => {
    if (arr.indexOf(item) === index) {
        arr2.push(item)
    }
})
console.log(arr2); //[ 1, 4, 3, 2, 5, 9 ]

方式二：使用includes()

let arr1 = [1, 4, 4, 3, 1, 2, 5, 5, 9, 1]
let arr2 = []
arr1.forEach(item => {
    if (!arr2.includes(item)) {
        arr2.push(item)
    }
})
console.log(arr2); //[ 1, 4, 3, 2, 5, 9 ]

方式三：使用indexOf()

let arr1 = [1, 4, 4, 3, 1, 2, 5, 5, 9, 1]
let arr2 = []
arr1.forEach(item => {
    if (arr2.indexOf(item) < 0) {
        arr2.push(item)
    }
})
console.log(arr2); //[ 1, 4, 3, 2, 5, 9 ]

方式四：使用es6的Set()

let arr1 = [1, 4, 4, 3, 1, 2, 5, 5, 9, 1]
let arr2 = []
// Set()去自动去除重复项
arr2 = [...new Set(arr1)]
console.log(arr2); //[ 1, 4, 3, 2, 5, 9 ]