VueJS - Interpolate a string within a string

Question

In VueJS, is there a way to interpolate a string within a string, either in the template or in the script? For example, I want the following to display 1 + 1 = 2 instead of 1 + 1 = {{ 1 + 1 }}.

<template>
    {{ myVar }}
</template>

<script>
    export default {
        data() {
            "myVar": "1 + 1 = {{ 1 + 1 }}"
        }
    }
</script>

Edit: to better illustrate why I would need this, here's what my actual data looks like:

section: 0,
sections: [
    {
        inputs: {
            user: {
                first_name: {
                    label: "First Name",
                    type: "text",
                    val: ""
                },
                ...
            },
            ...
        },
        questions:  [
            ...
            "Nice to meet you, {{ this.section.inputs.user.first_name.val }}. Are you ...",
            ...
        ]
    },
    ...
],

this.section.inputs.user.first_name.val will be defined by the user. While I could rebuild the question properties as computed properties, I would rather keep the existing data structure in tact.

"myVar": "1 + 1 = "+(1+1)? But why? You might be approaching it the wrong way, tell us the actual thing you are trying to achieve, there might be a better way. — Mat J
– Mat J, Commented Aug 28, 2018 at 16:44
I didn't explain the situation well. I have a complex data structure in which variables are built by referencing other variables, such as a sentence containing a user's name. I'm trying avoid a situation where I have to hard-code each sentence in the template, e.g. <p>Hello, {{ user.first_name }}</p> and am looking for a solution that would allow this instead: <p>{{ sentence }}</p>, where sentence = Hello, {{ this.user.first_name }}. — americanknight
– americanknight, Commented Aug 28, 2018 at 16:57
Cool, The right way to do this kind of thing would be to use computed properties — Mat J
– Mat J, Commented Aug 28, 2018 at 17:01
Thanks. That would work for me normally, but in my particular case, I need to first evaluate strings that refer to child variables before computing parent variables. I posted a solution that worked for me. — americanknight
– americanknight, Commented Aug 28, 2018 at 18:00
"child variables before computing parent variables" - Can you explain this further? I'm not able to understand what is parent and child here. — Mat J
– Mat J, Commented Aug 28, 2018 at 18:14

americanknight · Accepted Answer · 2018-08-28 17:58:03Z

3

I found the solution I was looking for from https://forum.vuejs.org/t/evaluate-string-as-vuejs-on-vuejs2-x/20392/2, which provides a working example on JsFiddle: https://jsfiddle.net/cpfarher/97tLLq07/3/

<template>
    <div id="vue">
        <div>
            {{parse(string)}}
        </div>
    </div>
</template>

<script>
    new Vue({
        el:'#vue',
        data:{
            greeting:'Hello',
            name:'Vue',
            string:'{{greeting+1}} {{name}}! {{1 + 1}}'
        },
        methods:{
            evalInContext(string){
                try{
                    return eval('this.'+string)
                } catch(error) {
                    try {
                        return eval(string)
                    } catch(errorWithoutThis) {
                        console.warn('Error en script: ' + string, errorWithoutThis)
                        return null
                    }
                }
            },
            parse(string){
                return string.replace(/{{.*?}}/g, match => {
                    var expression = match.slice(2, -2)
                    return this.evalInContext(expression)
                })
            }
        }
    })
</script>

answered Aug 28, 2018 at 17:58

americanknight

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4 Comments

Sphinx Over a year ago

I don't think it will support string:'{{greeting+name}}

Mat J Over a year ago

Can you provide your actual use case as I'm interested in knowing where computed property fails short? In the case shown here, a simple computed property seems to be perfectly capable.

americanknight Over a year ago

This solution works for me. I expanded my question with a more in-depth example of what my data structure looks like.

Lim Socheat Over a year ago

the solution is helpful.

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