js 数组去重方法汇总

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        title>js 数组去重title>
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        script src="https://cdn.bootcss.com/lodash.js/4.17.10/lodash.min.js">script>
        script type="text/javascript">
            //方法一
            function arrayUnique1(arr) {
                const ret = []
                for(let i = 0; i  arr.length; i++) {
                    const item = arr[i],
                        idx = ret.indexOf(item)

                    if(idx  0) {
                        ret.push(item)
                    }
                }
                return ret
            }
            //方法二
            function arrayUnique2(arr) {
                const map = {},
                    ret = []
                for(let i = 0; i  arr.length; i++) {
                    const item = arr[i]
                    if(map[item] == null) {
                        map[item] = i
                        ret.push(item)
                    }
                }
                return ret
            }
            //方法三：
            function arrayUnique3(arr) {
                return arr.filter((item, i) => arr.indexOf(item) === i)
            }
            //方法四
            function arrayUnique4(arr) {
                return [...new Set(arr)]
            }
            const arr = [1, 3, 1, 2, 2, 4, 3, 4, 1]
            console.log(arrayUnique4(arr))
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