javascript - "IF textTrue ELSE textFalse"的正则表达式

Question

我有两个字符串:

"~if~ text_if_true ~end~"
"~if~ text_if_true ~else~ text_if_false ~end~"

我想要的只是一个具有以下输出的正则表达式:

对于 1.=>

group 1 = text_if_true

对于 2.=>

group 1 = text_if_true, group 2 = text_if_false

我试过:

~if~(.*?)(?:~else~)(.*?)~end~

在 II 上工作正常但在 I 上不行，因为需要 ~else~

如果我用

~if~(.*?)(?:~else~)?(.*?)~end~   

在 (?:~else~) 后面有一个 ? (对于 0 或 1 个匹配项) text_if_true 和 text_if_false 在第一组。

有解决问题的简单方法吗？

const regex = /~if~(.*?)(?:~else~)(.*?)~end~/gm;
const regex2 = /~if~(.*?)(?:~else~)?(.*?)~end~/gm;

const str = `~if~ text_if_true ~else~ text_if_false ~end~
~if~ text_if_true ~end~`;
let m;


console.log('without ? quantifier')
while ((m = regex.exec(str)) !== null) {
    // This is necessary to avoid infinite loops with zero-width matches
    if (m.index === regex.lastIndex) {
        regex.lastIndex++;
    }
    
    // The result can be accessed through the `m`-variable.
    m.forEach((match, groupIndex) => {
        console.log(`Found match, group ${groupIndex}: ${match}`);
    });
}

console.log('with ? quantifier')
while ((m = regex2.exec(str)) !== null) {
    // This is necessary to avoid infinite loops with zero-width matches
    if (m.index === regex.lastIndex) {
        regex.lastIndex++;
    }
    
    // The result can be accessed through the `m`-variable.
    m.forEach((match, groupIndex) => {
        console.log(`Found match, group ${groupIndex}: ${match}`);
    });
}

Answer 1

与其让~else~这个词可选，不如让整个~else~(.*?)可选(我还添加了一些空格这样组就没有前导或尾随空格):

if~ (.*?)(?: ~else~ (.*?))? ~end

Demo