替换Javascript中正则表达式匹配的第n个实例
我正在尝试编写一个正则表达式函数,该函数将识别和替换字符串中匹配项的单个实例,而不会影响其他实例。例如,我有以下字符串:替换Javascript中正则表达式匹配的第n个实例,javascript,regex,Javascript,Regex,我正在尝试编写一个正则表达式函数,该函数将识别和替换字符串中匹配项的单个实例,而不会影响其他实例。例如,我有以下字符串: 12||34||56 12||34&&56 我想用符号替换第二组管道以获得此字符串: 12||34||56 12||34&&56 regex函数需要能够处理x个数量的管道,并允许我替换第n组管道,因此我可以使用相同的函数进行这些替换: 23||45||45||56||67 -> 23&&45||45||56||67
12||34||56
12||34&&56
我想用符号替换第二组管道以获得此字符串:
12||34||56
12||34&&56
regex函数需要能够处理x个数量的管道,并允许我替换第n组管道,因此我可以使用相同的函数进行这些替换:
23||45||45||56||67 -> 23&&45||45||56||67
23||34||98||87 -> 23||34||98&&87
我知道我可以在管道处拆分/替换/合并字符串,我还知道我可以在
/\\\\\\\\\\\\\/
上进行匹配并遍历结果数组,但我想知道是否有可能编写一个表达式来实现这一点。请注意,这是针对Javascript的,因此可以在运行时使用eval()
生成正则表达式,但不可能使用任何特定于Perl的正则表达式指令。以下是一些有效的方法:
"23||45||45||56||67".replace(/^((?:[0-9]+\|\|){n})([0-9]+)\|\|/,"$1$2&&")
其中n是小于第n个管道的一个(当然,如果n=0,则不需要第一个子表达式)
如果您想要一个函数来执行此操作:
function pipe_replace(str,n) {
var RE = new RegExp("^((?:[0-9]+\\|\\|){" + (n-1) + "})([0-9]+)\|\|");
return str.replace(RE,"$1$2&&");
}
更通用的函数
我遇到了这个问题,尽管标题非常笼统,但公认的答案只处理问题的特定用例
我需要一个更通用的解决方案,所以我写了一个,并想在这里分享
用法
此函数要求您向其传递以下参数:
:正在搜索的字符串original
:要搜索的字符串或带有捕获组的RegExp。如果没有捕获组,它将抛出错误。这是因为函数调用原始字符串上的模式
,并且split
:要查找的顺序事件;例如,如果您想要第二个匹配,请传入n
2
:用以替换匹配项的字符串,或接收匹配项并返回替换字符串的函数replace
String.prototype.replaceNthMatch = function(pattern, n, replace) {
// Same code as above, replacing "original" with "this"
};
"foo-bar-foo".replaceNthMatch("foo", 2, "baz"); // "foo-bar-baz"
通过测试
以下是此函数通过的Jasmine测试
describe("replaceNthMatch", function() {
describe("when there is no match", function() {
it("should return the unmodified original string", function() {
var str = replaceNthMatch("hello-there", /(\d+)/, 3, 'NEW');
expect(str).toEqual("hello-there");
});
});
describe("when there is no Nth match", function() {
it("should return the unmodified original string", function() {
var str = replaceNthMatch("blah45stuff68hey", /(\d+)/, 3, 'NEW');
expect(str).toEqual("blah45stuff68hey");
});
});
describe("when the search argument is a RegExp", function() {
describe("when it has a capture group", function () {
it("should replace correctly when the match is in the middle", function(){
var str = replaceNthMatch("this_937_thing_38_has_21_numbers", /(\d+)/, 2, 'NEW');
expect(str).toEqual("this_937_thing_NEW_has_21_numbers");
});
it("should replace correctly when the match is at the beginning", function(){
var str = replaceNthMatch("123_this_937_thing_38_has_21_numbers", /(\d+)/, 2, 'NEW');
expect(str).toEqual("123_this_NEW_thing_38_has_21_numbers");
});
});
describe("when it has no capture group", function() {
it("should throw an error", function(){
expect(function(){
replaceNthMatch("one_1_two_2", /\d+/, 2, 'NEW');
}).toThrow('RegExp must have a capture group');
});
});
});
describe("when the search argument is a string", function() {
it("should should match and replace correctly", function(){
var str = replaceNthMatch("blah45stuff68hey", 'stuff', 1, 'NEW');
expect(str).toEqual("blah45NEW68hey");
});
});
describe("when the replacement argument is a function", function() {
it("should call it on the Nth match and replace with the return value", function(){
// Look for the second number surrounded by brackets
var str = replaceNthMatch("foo[1][2]", /(\[\d+\])/, 2, function(val) {
// Get the number without the [ and ]
var number = val.slice(1,-1);
// Add 1
number = parseInt(number,10) + 1;
// Re-format and return
return '[' + number + ']';
});
expect(str).toEqual("foo[1][3]");
});
});
});
可能在IE7中不起作用
这段代码在IE7中可能会失败,因为该浏览器使用正则表达式错误地拆分字符串,如前所述。[与IE7握手]。我相信这就是解决办法;如果您需要支持IE7,祝您好运。:) 好极了!这应该是Node.js和Bower包。@vaughan-谢谢!如果你愿意的话,可以随意做一个。如果正则表达式包含多对括号怎么办?@principal-ideal-domain有一个很好的观点。我不能用这个,因为我的模式中有括号。我正试图找到一个修改的代码来修复这个问题,但我现在运气好。
describe("replaceNthMatch", function() {
describe("when there is no match", function() {
it("should return the unmodified original string", function() {
var str = replaceNthMatch("hello-there", /(\d+)/, 3, 'NEW');
expect(str).toEqual("hello-there");
});
});
describe("when there is no Nth match", function() {
it("should return the unmodified original string", function() {
var str = replaceNthMatch("blah45stuff68hey", /(\d+)/, 3, 'NEW');
expect(str).toEqual("blah45stuff68hey");
});
});
describe("when the search argument is a RegExp", function() {
describe("when it has a capture group", function () {
it("should replace correctly when the match is in the middle", function(){
var str = replaceNthMatch("this_937_thing_38_has_21_numbers", /(\d+)/, 2, 'NEW');
expect(str).toEqual("this_937_thing_NEW_has_21_numbers");
});
it("should replace correctly when the match is at the beginning", function(){
var str = replaceNthMatch("123_this_937_thing_38_has_21_numbers", /(\d+)/, 2, 'NEW');
expect(str).toEqual("123_this_NEW_thing_38_has_21_numbers");
});
});
describe("when it has no capture group", function() {
it("should throw an error", function(){
expect(function(){
replaceNthMatch("one_1_two_2", /\d+/, 2, 'NEW');
}).toThrow('RegExp must have a capture group');
});
});
});
describe("when the search argument is a string", function() {
it("should should match and replace correctly", function(){
var str = replaceNthMatch("blah45stuff68hey", 'stuff', 1, 'NEW');
expect(str).toEqual("blah45NEW68hey");
});
});
describe("when the replacement argument is a function", function() {
it("should call it on the Nth match and replace with the return value", function(){
// Look for the second number surrounded by brackets
var str = replaceNthMatch("foo[1][2]", /(\[\d+\])/, 2, function(val) {
// Get the number without the [ and ]
var number = val.slice(1,-1);
// Add 1
number = parseInt(number,10) + 1;
// Re-format and return
return '[' + number + ']';
});
expect(str).toEqual("foo[1][3]");
});
});
});