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<!DOCTYPE html>
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<title>Diggernaut: Documentation for Meta-Language | Other Commands | Eval</title>
<meta name="description" content="Executing fragments of JS code.">
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<h1>Other Commands</h1>
<div>
<h2>Eval</h2>
<p class="flow-text">
The <span class = "hlt">eval</span> command is intended for executing code written in other programming languages
(currently only JavaScript (ES5) is supported). It can only be executed in the context of the block, because it works with the register.
However, the command can return a value not only to the register, but can assign the values of variables in JS to digger variable also.
This feature allows you to receive several result values at once within one execution. If your JS code will work
for too long, it will be automatically interrupted. This is done to avoid misuse of this functionality.
</p>
<p class="flow-text">
Examples:
</p>
<pre class="language-yaml">
<code class="language-yaml"># RETURNING RESULT OF EXECUTION TO THE REGISTER
# PLEASE NOTE THAT IN THIS CASE
# JS CODE SHOULD BE USED INSIDE CLOSURE AND RETURN VALUE
- eval:
routine: js
body: "(function (){return new Date().getTime();})();"
</code></pre>
<pre class="language-yaml">
<code class="language-yaml"># MAP DIGGER VARIABLE `time` WITH JS VARIABLE `jstime` (VALUE OF time VARIABLE WILL BE SAME AS VALUE OF jstime)
- eval:
routine: js
body: "var jstime = new Date().getTime();"
assign:
time: jstime
</code></pre>
<p class="flow-text">
Usage examples:
</p>
<div class="row">
<div class="col s12">
<ul class="tabs excdark">
<li class="tab col s2"><a class="active" href="#eval_return">Return value</a></li>
<li class="tab col s2"><a href="#eval_assign">Map variables</a></li>
</ul>
</div>
<div id="eval_return" class="col s12">
<pre class="language-yaml">
<code class="language-yaml">- find:
path: body
do:
# EXECUTE JS CODE THAT RETURNS CURRENT DATE/TIME AS UNIX TIMESTAMP
- eval:
routine: js
body: "(function (){return new Date().getTime();})();"
# REGISTER VALUE: 1476403635606
</code></pre>
</div>
<div id="eval_assign" class="col s12">
<pre class="language-yaml">
<code class="language-yaml">- find:
path: body
do:
# EXECUTE JS CODE THAT ASSIGN CURRENT DATE/TIME AS UNIX TIMESTAMP
# TO JS VARIABLE `jstime` AND MAP IT TO DIGGER VARIABLE `time`
# YOU CAN MAP ANY NUMBER OF VARIABLES THIS WAY
- eval:
routine: js
body: "var jstime = new Date().getTime();"
assign:
time: jstime
- variable_get: time
# REGISTER VALUE: 1476403635606
</code></pre>
</div>
</div>
<p class="flow-text">
You can also use digger variables in JS code.
</p>
<p class="flow-text">
For example:
</p>
<pre class="language-yaml">
<code class="language-yaml">- find:
path: a
do:
- parse:
attr: href
- variable_set: link
- eval:
routine: js
body: "(function (){return '<%link%>' + '?time=' + new Date().getTime();})();"
# REGISTER VALUE: http://somelink.com/?time=1476403635606
# PLEASE NOTE THAT VARIABLE TAG IS ENCLOSED IN QUOTES
# SO JS INTERPRETER KNOWS THAT ITS A STRING
</code></pre>
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<p class="flow-text">
In the next chapter, we'll read about the commands for reloading and rereading pages.
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