JavaScript之数组拼接的效率高低

前言

简单证明下不同数组拼接的效率问题，下面上结果（注意：我只在谷歌浏览器上进行了测试）
先说结论：arr.concat(array) > arr.push > arr[i] > [...arr] > arr.concat(i)

正文

<script>
        // 测试数组拼接的效率问题
        let n = 500000
        function test1() {
            let test_s = +new Date()
            let arr = []
            for (let i = 0; i < n; i++) {
                arr[i] = i
            }
            let test_e = +new Date()
            console.log('index:'+ (test_e - test_s) + 'ms       lenth:' + arr.length)
        }
        function test2() {
            let test_s = +new Date()
            let arr = []
            for (let i = 0; i < n; i++) {
                arr.push(i)
            }
            let test_e = +new Date()
            console.log('push:'+ (test_e - test_s) + 'ms        lenth:' + arr.length)
        }
        let con_arr = []
        for (let i = 0; i < n; i++) {
            con_arr[i] = i
        }
        function test4() {
            let test_s = +new Date()
            let arr = []
            arr = arr.concat(con_arr)
            let test_e = +new Date()
            console.log('concat(arr):'+ (test_e - test_s) + 'ms     lenth:' + arr.length)
        }
        function test5() {
            let test_s = +new Date()
            let arr = []
            arr = [...arr, ...con_arr]
            let test_e = +new Date()
            console.log('es6...:'+ (test_e - test_s) + 'ms      lenth:' + arr.length)
        }
        test1()
        test2()
        test4()
        test5()
    </script>

下面是几组数据的测试结果

n=10000 n=100000 n=500000 n=1000000 n=5000000 n=10000000