修剪字符串中的特定字符

Question

什么是与此方法等效的JavaScriptC#:

var x = "|f|oo||"; 
var y = x.Trim('|'); //  "f|oo"

C#仅在字符串的开头和结尾处修剪所选字符!

Answer 1

一行就足够了:

var x = '|f|oo||';
var y = x.replace(/^\|+|\|+$/g, '');
document.write(x + '<br />' + y);

^\|+   beginning of the string, pipe, one or more times
|      or
\|+$   pipe, one or more times, end of the string

在一个功能:

function trim (s, c) {
  if (c === "]") c = "\\]";
  if (c === "\\") c = "\\\\";
  return s.replace(new RegExp(
    "^[" + c + "]+|[" + c + "]+$", "g"
  ), "");
}

chars = ".|]\\";
for (c of chars) {
  s = c + "foo" + c + c + "oo" + c + c + c;
  console.log(s, "->", trim(s, c));
}

Answer 2

Update: Was curious around the performance of different solutions and so I've updated a basic benchmark here: https://www.measurethat.net/Benchmarks/Show/12738/0/trimming-leadingtrailing-characters

Some interesting and unexpected results running under Chrome. https://www.measurethat.net/Benchmarks/ShowResult/182877

+-----------------------------------+-----------------------+
| Test name                         | Executions per second |
+-----------------------------------+-----------------------+
| Index Version (Jason Larke)       | 949979.7 Ops/sec      |
| Substring Version (Pho3niX83)     | 197548.9 Ops/sec      |
| Regex Version (leaf)              | 107357.2 Ops/sec      |
| Boolean Filter Version (mbaer3000)| 94162.3 Ops/sec       |
| Spread Version (Robin F.)         | 4242.8 Ops/sec        |
+-----------------------------------+-----------------------+

Please note; tests were carried out on only a single test string (with both leading and trailing characters that needed trimming). In addition, this benchmark only gives an indication of raw speed; other factors like memory usage are also important to consider.

If you're dealing with longer strings I believe this should outperform most of the other options by reducing the number of allocated strings to either zero or one:

+-----------------------------------+-----------------------+
| Test name                         | Executions per second |
+-----------------------------------+-----------------------+
| Index Version (Jason Larke)       | 949979.7 Ops/sec      |
| Substring Version (Pho3niX83)     | 197548.9 Ops/sec      |
| Regex Version (leaf)              | 107357.2 Ops/sec      |
| Boolean Filter Version (mbaer3000)| 94162.3 Ops/sec       |
| Spread Version (Robin F.)         | 4242.8 Ops/sec        |
+-----------------------------------+-----------------------+

Or if you want to trim from a set of multiple characters:

function trim(str, ch) {
    var start = 0, 
        end = str.length;

    while(start < end && str[start] === ch)
        ++start;

    while(end > start && str[end - 1] === ch)
        --end;

    return (start > 0 || end < str.length) ? str.substring(start, end) : str;
}

// Usage:
trim('|hello|world|', '|'); // => 'hello|world'

EDIT: For fun, trim words (rather than individual characters)

function trimAny(str, chars) {
    var start = 0, 
        end = str.length;

    while(start < end && chars.indexOf(str[start]) >= 0)
        ++start;

    while(end > start && chars.indexOf(str[end - 1]) >= 0)
        --end;

    return (start > 0 || end < str.length) ? str.substring(start, end) : str;
}

// Usage:
trimAny('|hello|world   ', [ '|', ' ' ]); // => 'hello|world'
// because '.indexOf' is used, you could also pass a string for the 2nd parameter:
trimAny('|hello| world  ', '| '); // => 'hello|world'

Answer 3

如果我理解得很好,你只想在字符串的开头或结尾处删除特定字符(例如:"|| fo || oo ||||"应该变为"foo || oo") .您可以创建ad hoc函数,如下所示:

function trimChar(string, charToRemove) {
    while(string.charAt(0)==charToRemove) {
        string = string.substring(1);
    }

    while(string.charAt(string.length-1)==charToRemove) {
        string = string.substring(0,string.length-1);
    }

    return string;
}

我用下面的代码测试了这个函数:

var str = "|f|oo||";
$( "#original" ).html( "Original String: '" + str + "'" );
$( "#trimmed" ).html( "Trimmed: '" + trimChar(str, "|") + "'" );

Answer 4

您可以使用正则表达式,例如:

var x = "|f|oo||";
var y = x.replace(/^[\|]+|[\|]+$/g, "");
alert(y); // f|oo

更新:

如果您希望将其概括为函数,可以执行以下操作:

var escapeRegExp = function(strToEscape) {
    // Escape special characters for use in a regular expression
    return strToEscape.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, "\\$&");
};

var trimChar = function(origString, charToTrim) {
    charToTrim = escapeRegExp(charToTrim);
    var regEx = new RegExp("^[" + charToTrim + "]+|[" + charToTrim + "]+$", "g");
    return origString.replace(regEx, "");
};

var x = "|f|oo||";
var y = trimChar(x, "|");
alert(y); // f|oo

Answer 5

让这个问题保持最新:

这是我使用ES6扩展运算符选择正则表达式函数的方法.

function trimByChar(string, character) {
  const first = [...string].findIndex(char => char !== character);
  const last = [...string].reverse().findIndex(char => char !== character);
  return string.substring(first, string.length - last);
}

Answer 6

这可以一次修剪几个字符:

String.prototype.trimChars = function (c) {
  var re = new RegExp("^[" + c + "]+|[" + c + "]+$", "g");
  return this.replace(re,"");
}

var x = "|f|oo||"; 
x =  x.trimChars('|'); // f|oo

var y = "..++|f|oo||++..";
y = y.trimChars('|.+'); // f|oo

var z = "\\f|oo\\"; // \f|oo\

// For backslash, remember to double-escape:
z = z.trimChars("\\\\"); // f|oo

Answer 7

A regex-less version which is easy on the eye:

const trim = (str, chars) => str.split(chars).filter(Boolean).join(chars);

For use cases where we're certain that there's no repetition of the chars off the edges.

Answer 8

const trim = (str, char) => {
    let i = 0;
    let j = str.length-1;
    while (str[i] === char) i++;
    while (str[j] === char) j--;
    return str.slice(i,j+1);
}
console.log(trim('|f|oo|', '|')); // f|oo

非正则表达式解决方案。两个指针：（i开始）和j（结束）。仅当指针匹配 char 时才移动指针，不匹配时停止。返回剩余的字符串。