40 lines
1.4 KiB
Markdown
40 lines
1.4 KiB
Markdown
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title = "Eww expressions"
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slug = "Embedded eww expression language"
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weight = 5
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+++
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# The embedded Eww expression-language
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Within variable references, you can make use of a small, built-in expression language.
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This can be used whereever you can use variable-references (`{{varname}}`).
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## Example
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```xml
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<button
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class="{{if button_active then 'active' else 'inactive'}}"
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onclick="toggle_thing">
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{{if button_active then 'disable' else 'enable'}}
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</button>
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Some math: {{12 + 2 * 10}}
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```
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## Syntax
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The expression language supports:
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- simple mathematical operations (`+`, `-`, `*`, `/`, `%`)
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- comparisons (`==`, `!=`, `>`, `<`)
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- boolean operations (`||`, `&&`, `!`)
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- elvis operator (`?:`)
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- if the left side is `""`, then returns the right side, otherwise evaluates to the left side.
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- conditionals (`if condition then 'value' else 'other value'`)
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- numbers, strings, booleans and variable references (`12`, `'hi'`, `true`, `some_variable`)
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- strings can contain other expressions again: `'foo {{some_variable}} bar'`
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- json access (`object.field`, `array[12]`, `object["field"]`)
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- for this, the object/array value needs to refer to a variable that contains a valid json string.
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- some function calls:
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- `round(number, decimal_digits)`: Round a number to the given amount of decimals
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- `replace(string, regex, replacement)`: Replace matches of a given regex in a string
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