v-bind is a VueJS directive used to dynamically bind one or more attributes, or a component prop to an expression.
Dynamic values to HTML attributes
The v-bind directive can be used to reactively update an HTML attribute.
- Syntax:
v-bind:attribute_name='value'
- Example, dynamically set the
src attribute of a <img> tag:
<div id='demo'>
<img v-bind:src='img' alt='Image' />
</div>
<script>
var vm = new Vue({
el: '#demo',
data: {img:'/imgs/dolphin.jpg'}
});
</script>
VueJS also provides a shorthand for
v-bind, it is replaced by the two-point character ":", as follows.
<img :src='img'/>
We can also bind an object of attributes to a single
v-bind.
<tag_name v-bind='{attribute_1:variable_1, attribute_2:variable_2}'>Content</tag_name>
- In the following example we dynamically set the
src and
class attributes with one
v-bind:
<style'>
.st_img {
border: 7px solid #e0e000;
height:110px;
margin:35px 2px 2px 20px;
transform: rotate(40deg);
}
</style>
<div id='demo'>
<img v-bind='{src:img, class:im_cls}' alt='Image'/>
</div>
<script>
var vm = new Vue({
el: '#demo',
data: {
img:'/imgs/dolphin.jpg',
im_cls:'st_img'
}
});
</script>
Binding HTML Style and Classes
When the v-bind is used to bind the class or style attribute, it supports additional value types such as Array or Objects.
Examples with html style
<div :style="{ fontSize: size + 'px' }"></div>
<div :style='[style_obj1, style_obj2]'></div>
Examples with html class
<div :class='{ red: is_red }'></div>
<div :class='[class_a, class_b]'></div>
<div :class='[class_a, { class_b: is_b, class_c: is_c }]'></div>
- For more details about binding html style and class, see the tutorial:
Class and Style with Vue.js
Dynamic attributes with v-bind
We can use dynamic arguments, by wrapping it with square brackets.
- Syntax:
<img v-bind:[attr_name]='value'/>
// shorthand
<img :[attr_name]='value'/>
- In the following example we dynamically set an ID attribute to an image:
<style'>
#im_rot {
border: 7px solid #ffbe00;
height:110px;
margin:35px 2px 2px 20px;
transform: rotate(40deg);
}
</style>
<div id='demo'>
<img :src='img' :[attr]='atr_val' alt='Image'/>
</div>
<script>
var vm = new Vue({
el: '#demo',
data: {
img:'/imgs/dolphin.jpg',
attr:'id',
atr_val:'im_rot'
}
});
</script>
v-bind and Components
v-bind can be used to pass data from parent to child components, using props property.
- Syntax:
<component_name :prop='item'></component_name>
- In the following example we bind the
text variable in component parent to pass its value from Vue instance to component's template:
<div id='demo'>
<comp_h :text='ar_txt[0]'></comp_h>
<comp_h :text='ar_txt[2]'></comp_h>
</div>
<script>
// Define a new component called comp_h
Vue.component('comp_h', {
props: ['text'],
template: '<h3>{{text}}</h3>'
});
//array with data for text in component
const ar_t =['Peace is good.', 'I`m wise.', 'I Keep and give my peace.'];
// Create a Vue instance
new Vue({
el: '#demo',
data:{
ar_txt: ar_t
}
});
</script>
- For more details about Vue components, see the tutorial:
Vue JS Components