如何在特定的索引范围内替换？

Question

我有一个这样的字符串：

var str = "this is test1
           this is test2
           this is test3
           this is test4";

现在我想在此范围之间的每一行之前附加 4 个空格：[14 - 40]。所以我想要这个输出：

var str = "this is test1
               this is test2
               this is test3
           this is test4";

换句话说，我想将此替换应用于特定范围：

var output = str.replace(/^(.*)$/gm, "    $1");

但是如你所知，上面的代码替换了所有字符串的正则表达式，那么，我怎样才能将它限制在特定的位置？

Answer 1

您可以将replace 与callback 一起使用：

var str = "this is test1\n"+
           "this is test2\n"+
           "this is test3\n"+
           "this is test4";

var posStart = 14; // start index
var posEnd   = 40; // end index
var re = new RegExp(
  '^([\\s\\S]{' + (posStart-1) + '})([\\s\\S]{' + (posEnd-posStart+1) + '})');
//=> re = /^([\s\S]{13})([\s\S]{27})/

var r = str.replace(re, function($0, $1, $2) {
    return $1+$2.replace(/\n/g, '\n    '); });

console.log(r);
/* 
"this is test1
    this is test2
    this is test3
this is test4"
*/

正则表达式 ^([\s\S]{13})([\s\S]{27}) 确保仅在位置 14-40 之间发生替换。

Answer 2

你可以试试这样的：

另外请注意，它不是检查 char 逻辑索引的好选择。

function addSpaces(){
  var str = "this is test1\n"+
            "this is test2\n"+
            "this is test3\n"+
            "this is test4"
  var data = str.split("\n");
  
  var result = data.map(function(item, index){
    if(index >0 && index < data.length-1){
      item = "    " + item;
    }
    return item;
  }).join("\n");
  
  console.log(result)
}

addSpaces();