JavaScript数组如何求和

    var sum = 0;
    console.time("for");
    for (var i = 0; i < arr.length; i++) {
        sum += arr[i];
    }
    console.timeEnd("for");
    console.log(sum);

    var sum = 0;
    function getSum(item, index, array) {
        sum += item;
    }
    console.time();
    arr.forEach(getSum);
    console.timeEnd();
    console.log(sum);

    var sum = 0;
    function getSum(item, index, array) {
        sum += item;
    }
    console.time();
    arr.some(getSum);
    console.timeEnd();
    console.log(sum);

    var sum = 0;
    function getSum(item, index, array) {
        sum += item;
    }
    console.time();
    arr.map(getSum);
    console.timeEnd();
    console.log(sum);

    var sum = 0;
    function getSum(item, index, array) {
        sum += item;
    }
    console.time();
    arr.filter(getSum);
    console.timeEnd();
    console.log(sum);