JavaScript 代码不断重复语句。我怎样才能阻止这个？答案

【问题标题】：JavaScript code keeps repeating statements. How can I stop this?JavaScript 代码不断重复语句。我怎样才能阻止这个？
【发布时间】：2019-01-14 06:17:09
【问题描述】：

我正在创建一个为期 12 天的圣诞节 javascript 程序，当我打印出声明时，它不断重复声明。你能给我一些关于如何解决这个问题并让程序正常工作的建议吗？

var day = ["first", "second", "third", "fourth", "fifth", "sixth", 
"seventh", "eighth", "ninth", "tenth", "eleventh", "twelfth"];
var song = "";

for (var x = 0; x <= 13; x++) {
song += "On the " + day[x] + " day of Christmas";
song += " my true love gave to me: ";

if (x == 0) {
    song += "a partridge in a pear tree."
} 
else {
    switch (x) {
        case 12:
            song += ("twelve drummers drumming, ");
        case 11:
            song += ("eleven pipers piping, ");
        case 10:
            song += ("ten lords a-leping, ");
        case 9:
            song += ("nine ladies dancing, ");
        case 8:
            song += ("eight maids a-milking, ");
        case 7:
            song += ("seven swans a-swimming, ");
        case 6:
            song += ("six geese a-laying, ");
        case 5:
            song += ("five gold rings,");
        case 4:
            song += ("four calling birds, ");
        case 3:
            song += ("three french hens, ");
        case 2:
            song += ("two turtle doves ");
        case 1:
            song += ("and a partridge in a pear tree.");
            break;
    }
}
console.log(song);}

【问题讨论】：

您可以为您的 switch case 字符串创建和等效数组，并删除 switch case，然后从该数组中使用

标签： javascript

【解决方案1】：

switch case 中缺少 break 语句。

switch (x) {
        case 12:
            song += ("twelve drummers drumming, ");
            break;
        case 11:
            song += ("eleven pipers piping, ");
            break;
        case 10:
            song += ("ten lords a-leping, ");
            break;
        case 9:
            song += ("nine ladies dancing, ");
            break;
        case 8:
            song += ("eight maids a-milking, ");
            break;
        case 7:
            song += ("seven swans a-swimming, ");
            break;
        case 6:
            song += ("six geese a-laying, ");
            break;
        case 5:
            song += ("five gold rings,");
            break;
        case 4:
            song += ("four calling birds, ");
            break;
        case 3:
            song += ("three french hens, ");
            break;
        case 2:
            song += ("two turtle doves ");
            break;
        case 1:
            song += ("and a partridge in a pear tree.");
            break;
    }

【讨论】：

【解决方案2】：

在您的 switch 语句中，您错过了 break 语句。你也可以将x==0 case 放在 switch 本身上，不需要单独的 if 语句。

【讨论】：

【解决方案3】：

您的 switch 语句需要在 case 中进行中断，并且 song 变量需要在循环开始时设置为空，而且您的 switch case 需要从零开始，以便每次都能获得正确的 case：

for (var x = 0; x < 12; x++) {
    song = "";    
    song += "On the " + day[x] + " day of Christmas";
    song += " my true love gave to me: ";

    if (x == 0) {
        song += "a partridge in a pear tree."
    } 
    else {
        switch (x) {
            case 11:
                song += ("twelve drummers drumming, ");
                break;
            case 10:
                song += ("eleven pipers piping, ");
                break;
            case 9:
                song += ("ten lords a-leping, ");
                break;
            case 8:
                song += ("nine ladies dancing, ");
                break;
            case 7:
                song += ("eight maids a-milking, ");
                break;
            case 6:
                song += ("seven swans a-swimming, ");
                break;
            case 5:
                song += ("six geese a-laying, ");
                break;
            case 4:
                song += ("five gold rings,");
                break;
            case 3:
                song += ("four calling birds, ");
                break;
            case 2:
                song += ("three french hens, ");
                break;
            case 1:
                song += ("two turtle doves ");
                break;
            case 0:
                song += ("and a partridge in a pear tree.");
                break;
            default:
        }
    }
    console.log(song);
}

【讨论】：

【解决方案4】：

var day = ["first", "second", "third", "fourth", "fifth", "sixth", 
"seventh", "eighth", "ninth", "tenth", "eleventh", "twelfth"];
var dayMessages = ["a partridge in a pear tree.", "and a partridge in a pear tree.", "two turtle doves ", "three french hens, ", "four calling birds, ", "five gold rings,", "six geese a-laying, ", 
"seven swans a-swimming, ", "eight maids a-milking, ", "ten lords a-leping, ", "ten lords a-leping, ", "eleven pipers piping, ", "twelve drummers drumming, "];
var song = "";

for (var x = 0; x <= 13; x++) {
  song = "On the " + day[x] + " day of Christmas";
  song += " my true love gave to me: ";
  song += dayMessages[x];

  console.log(song);
}

【讨论】：