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| Sometimes, it is desirable to use a multi line string in JavaScript, such as when adding css styles.
| | Modern browsers (including Firefox since version 34) support [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals template literals] which can span lines. |
| Here are some approaches, and discussion about the strengths and weaknesses of each approach.
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| == Concatenation ==
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| The basic method:
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| <pre class='sample'>
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| var longString = "Lorem ipsum dolor sit amet, " +
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| "venenatis penatibus etiam. " +
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| "Nec purus cras elit nec. " +
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| "Elit pharetra hymenaeos. " +
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| "Donec at cubilia pulvinar elit. " +
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| "Aliquet pretium tortor montes maecenas ante amet vel bibendum.";
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| </pre>
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| Pros:
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| * Simple to understand.
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| Cons:
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| * Extra syntax at the head and tail of every line.
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| * JavaScript string concatenation has poor performance characteristics.
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| A very similar but more efficient approach would define an array of many strings, then join them into one long string:
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| <pre class='sample'>
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| var longString = ["Lorem ipsum dolor sit amet, ",
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| "venenatis penatibus etiam. ",
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| "Nec purus cras elit nec. ",
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| "Elit pharetra hymenaeos. ",
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| "Donec at cubilia pulvinar elit. ",
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| "Aliquet pretium tortor montes maecenas ante amet vel bibendum."
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| ].join("");
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| </pre>
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| == Line continuation ==
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| JavaScript can continue lines, via trailing backslashes, like C:
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| <pre class='sample'>
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| var longString = "Lorem ipsum dolor sit amet, \
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| venenatis penatibus etiam. \
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| Nec purus cras elit nec. \
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| Elit pharetra hymenaeos. \
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| Donec at cubilia pulvinar elit. \
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| Aliquet pretium tortor montes maecenas ante amet vel bibendum.";
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| </pre>
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| Pros:
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| * Efficient.
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| Cons:
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| * An uncommon technique, therefore not as well understood.
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| * Requires extra syntax, albeit not as much as with concatenation.
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| == Using <tt>@resource</tt> ==
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| If the string is too long or too big — e.g. CSS code, JSON data — you can use [[Metadata Block#@resource|<tt>@resource</tt>]] metadata in your script and get its content using [[GM_getResourceText|<tt>GM_getResourceText</tt>]] API.
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| First, add <code>@resource</code> in metadata block
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| <nowiki>// @resource resourceName http://www.example.com/example.ext</nowiki>
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| You can then do something like
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| alert(GM_getResourceText("resourceName"));
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| GM_addStyle(GM_getResourceText("resourceName")); // if resource content is CSS
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| element.innerHTML = GM_getResourceText("resourceName"); // if resource content is HTML
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| var data = JSON.parse(GM_getResourceText("resourceName")); // if resource content is JSON
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| or whatever.
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| Pros:
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| * Editor syntax highlighting will work.
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| Cons:
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| * Requires file to be downloaded at install time.
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| * Low cross-platform compatibility.
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| [[Category:Coding Tips:General]] | | [[Category:Coding Tips:General]] |
Modern browsers (including Firefox since version 34) support template literals which can span lines.
