Question

我有一个元素数组，我需要使用java脚本添加每个第一，七，十三和十九（70,74,50,70）个值和它们的总和。

var rowSpanHeight = ['70', '70', '70', '70', '70', '70','74', '74', '74', '74', '74', '74','50', '50', '50', '50', '50', '50','70', '70', '70', '70', '70', '70'];

任何人都可以提供帮助？谢谢！

Answer 1

我从你的问题中假设你必须在阵列发生变化时添加它们，在这种情况下你可以使用：

function sumIfDifferent( inputArr ) {
    var lastNum = -1;
    var total = 0;
    for (var i = 0, l = inputArr.length; i < l; i++) {
        num = parseInt(inputArr[i], 10);
        if (num != lastNum) {
            lastNum = num;
            total+=num;
        }
    }
    return total;
}

alert(sumIfDifferent(['70', '70', '70', '70', '70', '70','74', '74', '74', '74', '74', '74','50', '50', '50', '50', '50', '50','70', '70', '70', '70', '70', '70']));

Answer 2

只需添加它们：

＆＃13;

var rowSpanHeight = ['70', '70', '70', '70', '70', '70','74', '74', '74', '74', '74', '74','50', '50', '50', '50', '50', '50','70', '70', '70', '70', '70', '70'];
document.write(parseInt(rowSpanHeight[0]) + parseInt(rowSpanHeight[6]) + parseInt(rowSpanHeight[12]) + parseInt(rowSpanHeight[18]));

＆＃13;

Answer 3

一个简单的方法是 -

  var rowSpanHeight = ['70', '70', '70', '70', '70', '70','74', '74', '74', '74', '74', '74','50', '50', '50', '50', '50', '50','70', '70', '70', '70', '70', '70'];
    var sum = ~~rowSpanHeight [0] + ~~rowSpanHeight [6] + ~~rowSpanHeight [12] + ~~rowSpanHeight [18];
    console.log(sum);

注意：这里使用~~（双波浪形）是一种将字符串转换为数字的快速方法，如果字符串为12.12则不会被用作~~将删除所有内容小数位后（很像parseInt）。有关https://stackoverflow.com/a/10841248/2737978

等SO问题的更多信息

Answer 4

这样的事可能有用......

var sum=0;
for(var a in rowSpanHeight){
    switch(a){
        case 0:
        case 6:
        case 12:
        case 18:
             sum+=parseInt(rowSpanHeight[a]);
        break;
    }
}

获取所有值的数组总和中的第n个值

4 个答案: