JavaScript - 字符串正则表达式反向引用
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JavaScript - string regex backreferences
提问by quano
You can backreference like this in JavaScript:
你可以在 JavaScript 中像这样反向引用：
var str = "123 $test 123";
str = str.replace(/($)([a-z]+)/gi, "");
This would (quite silly) replace "$test" with "test". But imagine I'd like to pass the resulting string of $2 into a function, which returns another value. I tried doing this, but instead of getting the string "test", I get "$2". Is there a way to achieve this?
这将（很愚蠢）用“test”替换“$test”。但是想象一下，我想将 $2 的结果字符串传递给一个函数，该函数返回另一个值。我尝试这样做，但我得到的不是字符串“test”，而是“$2”。有没有办法实现这一目标？
// Instead of getting "" passed into somefunc, I want "test"
// (i.e. the result of the regex)
str = str.replace(/($)([a-z]+)/gi, somefunc(""));
回答by SLaks
Like this:
像这样：
str.replace(regex, function(match, , , offset, original) { return someFunc(); })
回答by Sean
Pass a function as the second argument to replace:
将函数作为第二个参数传递给replace：
str = str.replace(/($)([a-z]+)/gi, myReplace);
function myReplace(str, group1, group2) {
return "+" + group2 + "+";
}
This capability has been around since Javascript 1.3, according to mozilla.org.
据mozilla.org 称，此功能自 Javascript 1.3 以来一直存在。
回答by vdegenne
Using ESNext, quite a dummy links replacer but just to show-case how it works :
使用 ESNext，一个相当虚拟的链接替换器，但只是为了展示它是如何工作的：
let text = 'Visit http://lovecats.com/new-posts/ and https://lovedogs.com/best-dogs NOW !';
text = text.replace(/(https?:\/\/[^ ]+)/g, (match, link) => {
// remove ending slash if there is one
link = link.replace(/\/?$/, '');
return `<a href="${link}" target="_blank">${link.substr(link.lastIndexOf('/') +1)}</a>`;
});
document.body.innerHTML = text;回答by 7ochem
If you would have a variable amount of backreferences then the argument count (and places) are also variable. The MDN Web Docsdescribe the follwing syntax for sepcifing a function as replacement argument:
如果您有可变数量的反向引用，那么参数计数（和位置）也是可变的。该MDN的Web文档描述了一个sepcifing功能替代参数的follwing语法：
function replacer(match[, p1[, p2[, p...]]], offset, string)
For instance, take these regular expressions:
例如，采用以下正则表达式：
var searches = [
'test([1-3]){1,3}', // 1 backreference
'([Ss]ome) ([A-z]+) chars', // 2 backreferences
'([Mm][a@]ny) ([Mm][0o]r[3e]) ([Ww][0o]rd[5s])' // 3 backreferences
];
for (var i in searches) {
"Some string chars and many m0re w0rds in this test123".replace(
new RegExp(
searches[i]
function(...args) {
var match = args[0];
var backrefs = args.slice(1, args.length - 2);
// will be: ['Some', 'string'], ['many', 'm0re', 'w0rds'], ['123']
var offset = args[args.length - 2];
var string = args[args.length - 1];
}
)
);
}
You can't use 'arguments' variable here because it's of type Argumentsand no of type Arrayso it doesn't have a slice()method.
你不能在这里使用 'arguments' 变量，因为它是类型Arguments而不是类型，Array所以它没有slice()方法。
回答by Hymansonkr
Note:Previous answer was missing some code. It's now fixed + example.
注意：上一个答案缺少一些代码。现在已修复 + 示例。
I needed something a bit more flexible for a regex replace to decode the unicode in my incoming JSON data:
我需要一些更灵活的正则表达式替换来解码传入 JSON 数据中的 unicode：
var text = "some string with an encoded 's' in it";
text.replace(/&#(\d+);/g, function() {
return String.fromCharCode(arguments[1]);
});
// "some string with an encoded 's' in it"
