The method of defining and using filters in Vue 2 is as follows: First, filters can be defined locally or globally, local filters can be declared in the component through filters object, and global filters are registered with Vue.filter() in the entry file; secondly, when calling, use the pipeline character |, such as {{ message | capitalize }}; secondly, filters can be passed, the first parameter is the value before the pipeline, and the rest are customized parameters, such as {{ price | formatCurrency('$') }}; multiple filters can also be connected in series for chain processing, such as {{ text | lowercase | capitalize }}; but note that filters cannot be used in v-model, it is recommended to use methods or computed instead of complex logic, and the filter function will be re-executeed every time you render.
Using filters (Filters) in Vue 2 is actually quite straightforward. As long as you master the basic structure and usage, you can easily handle text formatting and other operations in the template. Vue's filters are mainly used to format and output data, such as date, currency, string conversion, etc.
The following are several common usage scenarios to talk about how to use filters well.
How to define a filter
Vue 2 supports global or local definition of filters. The definition method is simple and the call is very convenient.
- Local filters : Only add
filtersobjects in component options are available in the current component:
export default {
filters: {
capitalize(value) {
if (!value) return ''
return value.charAt(0).toUpperCase() value.slice(1)
}
}
}- Global filter : All components can be registered in entry files (such as main.js):
Vue.filter('capitalize', function (value) {
return value.charAt(0).toUpperCase() value.slice(1)
})After defining it, you can use it in the template like this:
{{ message | capitalize }}How to pass parameters to filters
Sometimes you need to pass parameters to the filter, such as controlling the number of decimal places, specifying the date format, etc.
The syntax is like this:
{{ price | formatCurrency('$') }}The corresponding filter is written as follows:
filters: {
formatCurrency(value, symbol = '￥') {
return symbol value.toFixed(2)
}
}You can pass multiple parameters, but note that the first parameter is always the value in front of the pipe character.
Multiple filters are used in series
You can use multiple filters together, and the output of the previous filter is used as the input of the next one.
For example:
{{ text | lowercase | capitalize }} Suppose text = "HELLO" , after lowercase , it becomes "hello" , and then hand it capitalize , and finally output "Hello" .
This function is very practical when doing chain processing, but you need to pay attention to the order.
Common misunderstandings and precautions
Not available in v-model
Filters can only be used in interpolation expressions (i.e.{{ }}) andv-bind, and cannot be used inv-model.When the logic is complicated, it is recommended to use methods instead
If your processing logic is relatively complicated, such as conditional judgments, asynchronous requests, etc., it is best to use methods or computed attributes instead of filters.The filter does not cache the result
The filter function is re-executeed every time you re-render, so try to keep the filter lightweight.
Basically that's it. Although the filter of Vue 2 is not very powerful, it is still very convenient to do some simple format conversion in the display layer. As long as you don’t rely too much and use it reasonably, you can still improve development efficiency.
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