Javascript - 打破字符串文字......为什么？ [英] Javascript - breaking up string literals... why?

问题描述

对不起，问题标题太模糊了，但我正在查看Job posts board转换跟踪软件中的一些代码，并且第一次遇到这个问题。

I'm sorry the question title is so vague, but I was looking at some code from a Job posting boards conversion tracking software and ran across this for the first time.

    document.write('<i' + 'mg height="1" ' +
         'width="1" border="0" ' +
         'src="' + url + '&ifr' + 'ame=0" />');
    document.write('</ifr' + 'ame>');

为什么他们以这种方式分解字符串文字？具体来说，'< / ifr'+'ame>'

Why are they breaking up the string literal in this manner? Specifically '</ifr'+'ame>'

推荐答案

当HTML解析器看到某些标记时，即使嵌入在JavaScript字符串中，它们也会立即被解析为这些标记。

When HTML parsers see certain tags, even when embedded in JavaScript strings, they'll be parsed immediately as those tags.

打破它们可以避免这种行为 - < script> 通常会导致问题;我同意Mike的观点， iframe s（AFAIK也没有其他人也没有必要，但我无法与任何权威人士谈话）。

Breaking them up avoids this behavior--<script> is the one that usually causes problems; I agree with Mike that it shouldn't be necessary for iframes (AFAIK no others, either, but I can't speak to that with any authority).

这也是一种避免被抓取工具轻易解析的技巧。

It's also a trick to avoid being trivially parsed by crawlers.

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