The synergy between ternary operators and Vue filters

Recently, I came across a peculiar issue while working with Vue. Take a look at the code snippet from vue.html:

<label :text= 
    "$props.information ? (($props.information.primary || $props.information.secondary) | myFilter) : `No info`">
</label>

Surprisingly, this doesn't compile and Vue displays a warning:

[Vue warn]: Property or method "myFilter" is not defined on the instance but referenced during render. Make sure to declare reactive data properties in the data option.
(found in Root)

However, if we remove the ternary operator like so:

<label :text=
    "($props.information.primary || $props.information.secondary) | myFilter">
</label>

The code compiles without any issues and recognizes myFilter. It's worth noting that myFilter is defined in boot.ts. What could be causing this error specifically in the first example even though there seems to be no difference in scope?

Answer №1

The vertical bar symbolizes the bitwise-or operator in programming languages like JavaScript. In Vue, it has been tailored to function as a "pipe to filter" action within bindings. However, this interpretation seems to only apply when the vertical bar appears at the end of the binding expression, unlike with ternary usage where it can also be used in the middle.

Answer №2

The defined syntax for expressions is

(JavaScript expression) + (property | filters)
. It's important to note that filters can only be added to valid JavaScript code, so integrating filters into JavaScript directly is not feasible.

However, you can already utilize

$options.filters.myFilter(property)
within JavaScript expressions.

For more information, please visit: https://github.com/vuejs/vue/issues/5449#issuecomment-294337677

Answer №3

Here's what I suggest:

:text="

${props.data.main ? props.data.main : myFilter}
"

You could also try this:

:text="

${props.data ? props.data.main ? props.data.secondary : myFilter}
"

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