不生成新数组的迭代器方法：forEach()&every()&some()&reduce()&reduceRight()

    function square(num) {
        alert(num + " : " + num * num);
    }
    var nums = [ 1, 2, 3, 4 ];
    nums.forEach(square);

    function isEven(num) {
        return num % 2 == 0;
    }
    var nums = [ 2, 4, 6, 8, 10 ];
    var even = nums.every(isEven);
    if (even) {
        alert("all numbers are even");
    } else {
        alert("not all numbers are even");
    }

    function isEven(num) {
        return num % 2 == 0;
    }
    var nums = [ 1, 2, 3, 6, 7 ];
    var someEven = nums.some(isEven);
    if (someEven) {
        alert("some numbers are even");
    } else {
        alert("no numbers are even");
    }

    function add(runningTotal, currentValue) {
        return runningTotal + currentValue;
    }
    var nums = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ];
    var sum = nums.reduce(add);
    alert(sum); // 显示 55

    function concat(accumulatedString, item) {
        return accumulatedString + item;
    }
    var words = [ "the ", "quick ", "brown ", "fox " ];
    var sentence = words.reduce(concat);
    alert(sentence); // 显示 "the quick brown fox"

    function add(runningTotal, currentValue) {
        return runningTotal + currentValue;
    }
    var nums = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ];
    var sum = nums.reduceRight(add);
    alert(sum); // 显示 55

    function concat(accumulatedString, item) {
        return accumulatedString + item;
    }
    var words = [ "the ", "quick ", "brown ", "fox " ];
    var sentence = words.reduceRight(concat);
    alert(sentence); // 显示 "fox brown quick the"