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如何在javascript中使用前瞻实现负的前瞻?

  •  1
  • selfagency  · 技术社区  · 7 年前

    既然不能在JavaScript中使用负lookbehinds,那么如何使用lookahead或其他JavaScript支持的方法在没有负lookbehinds的情况下实现相同的正则表达式匹配呢?

    (?<!<\/strong>\n\s{4}|<\/strong>&nbsp;\n\s{4})<br>

    我想找到所有 <br> 不在前面的标记 </strong> </strong>&nbsp; 然后是换行符和一系列空格字符。

    Here's my code 和一些用于测试的示例文本。我用lookbehind在pcre中实现了它,但我不知道如何在JavaScript中实现它。

    我在这里尝试了其他示例,但我无法找出如何根据需要实施这些解决方案。

    Javascript lookbehind是 coming in ES2018

    2 回复  |  直到 6 年前
        1
  •  1
  •   KevBot    7 年前

    非正则表达式方法

    在解析HTML时,我更喜欢将HTML转换为DocumentFragments。这允许我使用常见的querySelector方法和JS函数来实现我的最终目标。

    我将3个br标记替换为以下内容: <div>REPLACED</div> html-fragment

    const html = `<p><strong>It was a weak bit.</strong>&nbsp;
        <br>Because it&rsquo;s already been done. If he had been like, &ldquo;I don&rsquo;t know, do you want to go to the La Brea tar pits and scoop some tar out and give ourselves a facial and burn ourselves and then only be able to know each other?&rdquo; I would be like, &ldquo;Haa, what?! Okay.&rdquo; I mean, something new is going on here. He basically did the equivalent of like when guys do &ldquo;fat guy in a little coat,&rdquo; and they act like it&rsquo;s not a Chris Farley callback. It&rsquo;s like, this is a joke that&rsquo;s in our system, so you&rsquo;re a little bit unoriginal or even worse, you don&rsquo;t know you&rsquo;re unoriginal.&nbsp;</p>
    <p><strong>Does he know it&rsquo;s you?</strong>&nbsp;
        <br>I do think he knew that I was a comedian named Jenny. So anyway, he&rsquo;s like, &ldquo;Let&rsquo;s go to the Renaissance fair,&rdquo; and I call my friends, and I&rsquo;m like, &ldquo;I&rsquo;m not going on this date.&rdquo; And they&rsquo;re like, &ldquo;Oh Jenny, come on, don&rsquo;t be so closed down, you need to get out there.&rdquo; I&rsquo;m like, &ldquo;UGH, fine.&rdquo; Then we have a series of text messages back and forth that I&rsquo;m just kind of like, <em>What is this? Is this what dating is like?</em> I was with my ex-husband for nine years, then I was in a very serious relationship that was passionate for a year, and I&rsquo;m like, I don&rsquo;t know, maybe I just don&rsquo;t know what&rsquo;s going on. And he&rsquo;s asking me these questions that I&rsquo;m like, What. The. Fuck. Why don&rsquo;t you just wait?</p>
    <p><strong>What is he asking you?</strong>&nbsp;
        <br>Like, &ldquo;Where was the last place you flew on an airplane?&rdquo; And I&rsquo;m not a rude or cruel woman, but I was like, I don&rsquo;t... dude... just wait. Sit me down, I&rsquo;ll tell you anything, just wait. Just wait until Saturday.</p>
    <p><strong>Also, that&rsquo;s the kind of question that is like, &ldquo;I&rsquo;m gonna go on the internet and search random questions to ask someone.&rdquo;</strong>&nbsp;
        <br>Yeah, it&rsquo;s not great. It&rsquo;s a real speed-dating question. I would love it in other circumstances if it was like a page in <em>Entertainment Weekly</em>, you know? So then I&rsquo;m like, &ldquo;I made us a reservation at this restaurant, will you meet me there?&rdquo; He&rsquo;s like, &ldquo;Yes, is it fancy?&rdquo; I&rsquo;m like, &ldquo;No,&rdquo; and he&rsquo;s like, &ldquo;Okay, should I wear something like this?&rdquo; And he sends me a picture of a knight&rsquo;s costume. Like from the Renaissance fair. At which point I&rsquo;m like what the fuck, dude? Because I didn&rsquo;t even jump on this riff in the first place. It&rsquo;s not like I was like, &ldquo;Yes, and I will wear my wench&#39;s costume and bring a cup of mead!&rdquo; I&rsquo;m just like... Heh?! What? Why are you doing this?</p>
    <p><strong>You didn&rsquo;t respond positively to the bit.</strong>
        <br>Never. Anyway, on the day of the date, I was like, &ldquo;How will I know it&rsquo;s you?&rdquo; And I thought he would be like, &ldquo;I&rsquo;m 6&rsquo;1&rdquo; and I&rsquo;ve got a beard,&rdquo; or some
    <p><br></p>
    <p><br></p>
    <p><br></p>`;
    
    const fragment = HtmlFragment(html);
    Array.from(fragment.querySelectorAll('br'))
      .filter(br => {
        let previous = br.previousElementSibling;
        return (previous === null || previous.nodeName !== 'STRONG');
      })
      .forEach(br => {
        let div = document.createElement('div');
        div.innerText = 'REPLACED';
        br.parentNode.replaceChild(div, br);
      });
    
    let div = document.createElement('div');
    div.appendChild(fragment);
    
    console.log(div.innerHTML);
    <script src="https://unpkg.com/html-fragment@1.1.0/lib/html-fragment.min.js"></script>
        2
  •  0
  •   user557597 user557597    7 年前

    你必须匹配它才能通过它。
    没有别的办法了!!!!

    /(<\/strong>\n\s{4}|<\/strong>&nbsp;\n\s{4})?<br>/

    https://regex101.com/r/xVJhGl/1

    var text =
    "<p><strong>It was a weak bit.</strong>&nbsp;\n"
    + "    <br>Because it&rsquo;s already been done. If he had been like, &ldquo;I don&rsquo;t know, do you want to go to the La Brea tar pits and scoop some tar out and give ourselves a facial and burn ourselves and then only be able to know each other?&rdquo; I would be like, &ldquo;Haa, what?! Okay.&rdquo; I mean, something new is going on here. He basically did the equivalent of like when guys do &ldquo;fat guy in a little coat,&rdquo; and they act like it&rsquo;s not a Chris Farley callback. It&rsquo;s like, this is a joke that&rsquo;s in our system, so you&rsquo;re a little bit unoriginal or even worse, you don&rsquo;t know you&rsquo;re unoriginal.&nbsp;</p>\n"
    + "<p><strong>Does he know it&rsquo;s you?</strong>&nbsp;\n"
    + "    <br>I do think he knew that I was a comedian named Jenny. So anyway, he&rsquo;s like, &ldquo;Let&rsquo;s go to the Renaissance fair,&rdquo; and I call my friends, and I&rsquo;m like, &ldquo;I&rsquo;m not going on this date.&rdquo; And they&rsquo;re like, &ldquo;Oh Jenny, come on, don&rsquo;t be so closed down, you need to get out there.&rdquo; I&rsquo;m like, &ldquo;UGH, fine.&rdquo; Then we have a series of text messages back and forth that I&rsquo;m just kind of like, <em>What is this? Is this what dating is like?</em> I was with my ex-husband for nine years, then I was in a very serious relationship that was passionate for a year, and I&rsquo;m like, I don&rsquo;t know, maybe I just don&rsquo;t know what&rsquo;s going on. And he&rsquo;s asking me these questions that I&rsquo;m like, What. The. Fuck. Why don&rsquo;t you just wait?</p>\n"
    + "<p><strong>What is he asking you?</strong>&nbsp;\n"
    + "    <br>Like, &ldquo;Where was the last place you flew on an airplane?&rdquo; And I&rsquo;m not a rude or cruel woman, but I was like, I don&rsquo;t... dude... just wait. Sit me down, I&rsquo;ll tell you anything, just wait. Just wait until Saturday.</p>\n"
    + "<p><strong>Also, that&rsquo;s the kind of question that is like, &ldquo;I&rsquo;m gonna go on the internet and search random questions to ask someone.&rdquo;</strong>&nbsp;\n"
    + "    <br>Yeah, it&rsquo;s not great. It&rsquo;s a real speed-dating question. I would love it in other circumstances if it was like a page in <em>Entertainment Weekly</em>, you know? So then I&rsquo;m like, &ldquo;I made us a reservation at this restaurant, will you meet me there?&rdquo; He&rsquo;s like, &ldquo;Yes, is it fancy?&rdquo; I&rsquo;m like, &ldquo;No,&rdquo; and he&rsquo;s like, &ldquo;Okay, should I wear something like this?&rdquo; And he sends me a picture of a knight&rsquo;s costume. Like from the Renaissance fair. At which point I&rsquo;m like what the fuck, dude? Because I didn&rsquo;t even jump on this riff in the first place. It&rsquo;s not like I was like, &ldquo;Yes, and I will wear my wench&#39;s costume and bring a cup of mead!&rdquo; I&rsquo;m just like... Heh?! What? Why are you doing this?</p>\n"
    + "<p><strong>You didn&rsquo;t respond positively to the bit.</strong>\n"
    + "    <br>Never. Anyway, on the day of the date, I was like, &ldquo;How will I know it&rsquo;s you?&rdquo; And I thought he would be like, &ldquo;I&rsquo;m 6&rsquo;1&rdquo; and I&rsquo;ve got a beard,&rdquo; or some\n"
    + "<p><br></p>\n"
    + "<p><br></p>\n"
    + "<p><br></p>\n"
    ;
    
    var rx = /(<\/strong>\n\s{4}|<\/strong>&nbsp;\n\s{4})?<br>/g;
    
    text = text.replace( rx , function(match, a)
        {
            if ( a )
                return match;
            return "<REPL>";
        }
    );
    
    console.log( text );