support use unReactivity data in Template

[zhangshichun]

What problem does this feature solve?

for example in render function:

const a = 'Hello world unReactivity'

export default {
render(c){
return c(div,[a])
}
}

here the a is not a reactivity data,but when we use template,it seems that we must make a to be a reactivity data?sometimes is not in need.

What does the proposed API look like?

<template>
<div>
{{ a }}
</div>
</template>
<script>
export default {
unReactivity:{
a: 'Hello world unReactivity'
}
}
</script>

[flyyang]

Try this:

const a = 'Hello world unReactivity'
export default {
  data () {
     return {
        a,
     }
  }
}

[zhangshichun]

Try this:

const a = 'Hello world unReactivity'
export default {
  data () {
     return {
        a,
     }
  }
}

now,the 'a' is reactivity. if 'a' is a big Object,performance overhead may be big;'computed' is a light choose,but if there are many 'a',is also a lot performance overhead.
so i wish has a method to use unReactivity data.

[Justineo]

Duplicate of #2637