如何删除 for 循环中的最后一个逗号？答案

【问题标题】：How can I remove the last comma in my for loop?如何删除 for 循环中的最后一个逗号？
【发布时间】：2019-09-02 15:41:12
【问题描述】：

function currentLine(katzDeliLine) {
    if (katzDeliLine.length > 0) {
        var textToPrint = "The line is currently: "

        for (var crrLine = 0; crrLine < katzDeliLine.length; crrLine++) {

            textToPrint = textToPrint + (crrLine + 1) + ". " + katzDeliLine[crrLine] + ","

        }


        return textToPrint;
    } else {
        return "The line is empty"
    }
}

var lineofpeople = ["katrina", "kevin", "vincent"]

输出是： The line is currently: 1. katrina, 2. kevin, 3. vincent,

我正在尝试去掉 'vincent' 之后的最后一个逗号

我尝试了 if 语句，也尝试了 .join() 方法。我不知道如何在代码中实现它们。

【问题讨论】：

欢迎，凯文。请take the tour.

标签： javascript arrays for-loop

【解决方案1】：

您可以将前导数字与值映射并用逗号连接数组。

function currentLine(array) {
    return array.length
        ? `The line is currently: ${array.map((v, i) => `${i + 1}. ${v}`).join(', ')}.`
        : "The line is empty.";
}

var lineofpeople = ["katrina", "kevin", "vincent"];

console.log(currentLine(lineofpeople));
console.log(currentLine([]));

【讨论】：

【解决方案2】：

一个简单的解决方案是使用 template literals 和 join()。

这里你应该注意它不是单引号，而是一个反引号。

var lineofpeople = ["katrina", "kevin", "vincent"]
const emptyLine = []

// Using arrow function; the code is short
const currentLine = (line) => {
  return !line.length ? 'The line is empty' : `The line is currently: ${line.map((e, i) => `${i + 1}. ${e}`).join(', ')}`
}

console.log(currentLine(lineofpeople)) // expected: The line is currently: 1. katrina, 2. kevin, 3. vincent

console.log(currentLine(emptyLine)) // expected: "The line is empty"

【讨论】：

【解决方案3】：

使用textToPrint.slice(0,-1)删除返回字符串的最后一部分

function currentLine(katzDeliLine) {
   if (katzDeliLine.length > 0) {
   var textToPrint = "The line is currently: "  

   for (var crrLine = 0;  crrLine < katzDeliLine.length; crrLine++) {
     textToPrint = textToPrint + (crrLine + 1)+". " +katzDeliLine[crrLine]+","
   }

   return textToPrint.slice(0,-1);
   } 
   else {
      return "The line is empty"
   }
}

 var lineofpeople = ["katrina", "kevin", "vincent"]
 console.log(currentLine(lineofpeople));

【讨论】：

【解决方案4】：

function currentLine(katzDeliLine) {
    if (katzDeliLine.length > 0) {
        var textToPrint = "The line is currently: "  

        for (var crrLine = 0;  crrLine < katzDeliLine.length; crrLine++) {

        textToPrint = textToPrint + (crrLine + 1)+". " 
        +katzDeliLine[crrLine]+","

}


return textToPrint.replace(/,\s*$/, "");
} else {
return "The line is empty"
}
}

var lineofpeople = ["katrina", "kevin", "vincent"]
console.log(currentLine(lineofpeople));

【讨论】：

【解决方案5】：

您可以使用正则表达式删除最后一个逗号

$ 用于匹配字符串的结尾

let line = 'string1, string2, string3, string4, string5,'

console.log(line.replace(/,$/g,''))

【讨论】：

【解决方案6】：

只检查当前索引是否是最后一个，如果是，不要加逗号：

for (var crrLine = 0; crrLine < katzDeliLine.length; crrLine++) {

        textToPrint = textToPrint + (crrLine + 1) + ". " + katzDeliLine[crrLine] + (crrLine != (katzDeliLine.length - 1) ? "," : "")

    }

【讨论】：