Question

我有一个带有if语句的函数，无论是否为真，该函数又应调用外部函数。我得到的结果是“未定义”。你能指出我正确的方向吗？

功能1：

function printRange(rangeStart, rangeStop) {
    let summa = [];

    for (i = rangeStart; i <= rangeStop; i++) {
        summa.push(i);
    }
    let result2 = summa.join();
    return result2;
}

功能2：

function printRangeReversed(rangeStart, rangeStop) {
    let summa = [];

    for (i = rangeStart; i >= rangeStop; i--) {
        summa.push(i);
    }
    let result3 = summa.join();
    return result3;
}

功能3：

function printAnyRange(rangeStart, rangeStop) {

    if (rangeStart < rangeStop) {
        printRange(rangeStart, rangeStop);
    } else {
        printRangeReversed(rangeStart, rangeStop);
    }
    return;
}

调用函数：printAnyRange(21, 45);

正如我所说，这一切对我来说似乎合乎逻辑，但我猜那不是因为我得到了“未定义”。

预期结果应为："21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45"

致谢。

Answer 1

您什么都不会退货。捕获函数的结果并返回该变量。

function printRange(rangeStart, rangeStop) {
    let summa = [];

    for (i = rangeStart; i <= rangeStop; i++) {
        summa.push(i);
    }
    let result2 = summa.join();
    return result2;
}

function printRangeReversed(rangeStart, rangeStop) {
    let summa = [];

    for (i = rangeStart; i >= rangeStop; i--) {
        summa.push(i);
    }
    let result3 = summa.join();
    return result3;
}

function printAnyRange(rangeStart, rangeStop) {
    let result = null;

    if (rangeStart < rangeStop) result = printRange(rangeStart, rangeStop);
    else result = printRangeReversed(rangeStart, rangeStop);
        
    return result;
}

console.log(printAnyRange(1,5));
console.log(printAnyRange(5,1));

Answer 2

从function test(element) { var objectID = element.id; ... }和function 1返回的值未被function 2使用或存储。尝试以下代码：

function 3

这应该可以解决问题。

Answer 3

您需要对返回的值进行处理，例如记录它们：

function printAnyRange(rangeStart, rangeStop) {

    if (rangeStart < rangeStop) {
        console.log(printRange(rangeStart, rangeStop));
    } else {
        console.log(printRangeReversed(rangeStart, rangeStop));
    }
    return;
}

或从主函数返回它们：

function printAnyRange(rangeStart, rangeStop) {

    if (rangeStart < rangeStop) {
        result = printRange(rangeStart, rangeStop);
    } else {
        result = printRangeReversed(rangeStart, rangeStop);
    }
    return result;
}

从函数内部的if语句调用函数

3 个答案: