Template Syntax Back
Templates used in Vue is like an extension of HTML, which allows us to declaratively bind data to the rendered DOM. For those templates, Vue has compiled them into Virtual DOM render functions, and figure out the minimal number of components to re-render through its reactivity system when states of components have been changed. (this design is familiar with React)
1. Interpolations (内插)
1.1 Text
The most basic form of data biding is text interpolation with using double braces:
<span>{{ message }}</span>
This interpolation will be updated when data has been modified, and if you want it to show with a consistent value during rendering, you can use v-once directive to do so:
<span v-once>consistent {{ message }}</span>
1.2 Raw HTML
Double braces interprets data as plain text, rather than HTML. If you want to inject HTML into an element, v-html directive is what you need (note: using v-html like dangerouslySetInnerHTML in React, will result in XSS vulnerabilities):
<span v-html="rawHTML"></span>
1.3 Attributes
In React, we can pass data through attributes with mustache style like following snippet:
<component id={data.id}></component>
It is unfortunate that Vue has not supported such a feature, and if we want to pass through, we may need to use v-bind:{attribute} directive to do so:
<component v-bind:id="data.id"></component>
In addition, boolean attributes may work a little differently:
<button v-bind:disabled="isDisabled"></button>
disabled attribute won't be included in the button when isDisabled has the value of null, undefined, or false.
1.4 Expressions
Full power of JavaScript expressions are supported inside all data bindings:
{{ 'abc' + message }}
<div v-bind:id="'list-' + data.id"></div>
But only when the expression is REAL and SINGLE (note: Math and Date are only two available global variable you can access):
<!-- not an expression -->
{{ const a = 1 }}
<!-- not a single expression -->
{{ if (true) { return message } }}
<!-- unavailable global variables -->
{{ window.navigator.userAgent }}
2. Directives
Directives are a kind of attributes named with v- prefix, which value is expected to be a single JavaScript expression, except for v-for. Their job is to apply side effects to the DOM when the values of theirs have been modified. For instance, v-if will remove/insert an element based on the turthiness of the value.
2.1 Arguments
Some directives can take an "argument" right following itself with a colon as a separator, like v-bind:{attribute}, v-on:{event}, etc.
2.2 Modifiers
Modifiers are special postfixes separated by a dot, which indicate that a directive should be bound in some special way, like .prevent, which has told the v-on directive to call event.preventDefault() while triggered:
<form v-on:submit.prevent="onSubmit"></form>
For more details of other modifiers, we can check here .
3. Shorthands
Even if the v- prefix help identifying Vue specific attributes in templates, sometimes we still feel that it is verbose to use frequently used directives. Therefore, Vue has provided two shorthands for two of the most often used directives, v-bind and v-on:
<!-- full syntax -->
<a v-bind:href="url">...</a>
<!-- shorthands -->
<a :href="url">...</a>
<!-- full syntax -->
<a v-on:click.prevent="handler">...</a>
<!-- shorthands -->
<a @click.prevent="handler">...</a>
Why using : or @? Maybe authors think that these are two valid characters for attribute names parsing under all Vue supported browsers.
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