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50 lines
1.8 KiB
Markdown
50 lines
1.8 KiB
Markdown
# JavaScript Transformation Service
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Transform an input to an output using JavaScript.
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It expects the transformation rule to be read from a file which is stored under the `transform` folder.
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To organize the various transformations, one should use subfolders.
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## Example
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Let's assume we have received a string containing `foo bar baz` and we're looking for a length of the last word (`baz`).
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transform/getValue.js:
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```
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(function(i) {
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var array = i.split(" ");
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return array[array.length - 1].length;
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})(input)
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```
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## Test JavaScript
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You can use online JavaScript testers to validate your script.
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E.g. https://www.webtoolkitonline.com/javascript-tester.html
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`Input` variable need to be replaced by the test string, e.g. earlier test string `foo bar baz`
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```
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(function(i) {
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var array = i.split(" ");
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return array[array.length - 1].length;
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})("foo bar baz")
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```
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When you press execute button, tester will show the result returned by the script or error if script contains any.
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## Usage as a Profile
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The functionality of this `TransformationService` can be used in a `Profile` on an `ItemChannelLink` too.
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To do so, it can be configured in the `.items` file as follows:
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```java
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String <itemName> { channel="<channelUID>"[profile="transform:JS", function="<filename>", sourceFormat="<valueFormat>"]}
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```
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The Javascript file (from within the `transform` folder) to be used has to be set in the `function` parameter.
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The parameter `sourceFormat` is optional and can be used to format the input value **before** the transformation, i.e. `%.3f`.
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If omitted the default is `%s`, so the input value will be put into the transformation without any format changes.
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Please note: This profile is a one-way transformation, i.e. only values from a device towards the item are changed, the other direction is left untouched.
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