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Extended description of r_variables in njs.
author Yaroslav Zhuravlev <yar@nginx.com>
date Thu, 05 Jan 2023 16:34:01 +0000
parents 3be061a0941a
children 16613b91c584
comparison
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2925:3be061a0941a 2926:237a77d8565b
7 <!DOCTYPE article SYSTEM "../../../../dtd/article.dtd"> 7 <!DOCTYPE article SYSTEM "../../../../dtd/article.dtd">
8 8
9 <article name="Reference" 9 <article name="Reference"
10 link="/en/docs/njs/reference.html" 10 link="/en/docs/njs/reference.html"
11 lang="en" 11 lang="en"
12 rev="94"> 12 rev="95">
13 13
14 <section id="summary"> 14 <section id="summary">
15 15
16 <para> 16 <para>
17 <link doc="index.xml">njs</link> provides objects, methods and properties 17 <link doc="index.xml">njs</link> provides objects, methods and properties
576 <tag-desc> 576 <tag-desc>
577 <link doc="../varindex.xml">nginx variables</link> object, writable 577 <link doc="../varindex.xml">nginx variables</link> object, writable
578 (since <link doc="changes.xml" id="njs0.2.8">0.2.8</link>). 578 (since <link doc="changes.xml" id="njs0.2.8">0.2.8</link>).
579 579
580 <para> 580 <para>
581 For example, to get the <literal>$foo</literal> variable,
582 one of the following syntax can be used:
583 <example>
584 r.variables['foo']
585 r.variables.foo
586 </example>
587 nginx treats variables referenced in <literal>nginx.conf</literal>
588 and unreferenced variables differently.
589 When a variable is referenced, it may be cacheable,
590 but when it is unreferenced it is always uncacheable.
591 For example, when the
592 <link doc="../http/ngx_http_core_module.xml" id="var_request_id">$request_id</link>
593 variable is only accessed from njs,
594 it has a new value every time it is evaluated.
595 But, when the
596 <link doc="../http/ngx_http_core_module.xml" id="var_request_id">$request_id</link>
597 is referenced, for example:
598 <example>
599 proxy_set_header X-Request-Id $request_id;
600 </example>
601 the <literal>r.variables.request_id</literal> returns the same value every time.
602 </para>
603
604 <para>
581 A variable is writable if: 605 A variable is writable if:
582 <list type="bullet"> 606 <list type="bullet">
583 607
584 <listitem> 608 <listitem>
585 it was created using the <literal>js_var</literal> directive for 609 it was created using the <literal>js_var</literal> directive for