javascript - 从函数内的 if 语句调用函数

Question

我有一个带有 if 语句的函数，无论是否为真，该函数都应该调用外部函数。我得到的结果是“未定义”。你能给我指出正确的方向吗？

函数一:

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

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

功能二:

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

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

功能三:

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，这一切对我来说都是合乎逻辑的，但我想这不是因为我得到了“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"

问候。

Answer 1

您没有返回任何东西。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));