DynamoDB Scan FilterExpression item IN list

list_in_filter.js

const listToObjectMappings = (list) => {
    let x = {}
    for (var i=0; i<list.length; i++){
        x[':' + i.toString()] = list[i]
    }
    return x
}

let statuses = ['available', 'in-transit', 'delivered']
let mappings = listToObjectMappings(statuses)

let type = 'delivery' // type is just to demonstrate the use of Object.assign to build the 'ExpressionAttributeValues'
let joined = Object.keys(mappings).join(); // string: ":available, :in-transit, :delivered"

query = {
    FilterExpression: '#type = :type AND #stat IN (' + joined + ')',
    ExpressionAttributeNames: {
        '#stat' : 'status',
        '#type' : 'type'
    },
    ExpressionAttributeValues: Object.assign( { ':type': type }, mappings )
}

At line 13:

let joined = Object.keys(mappings).join(); // string: ":available, :in-transit, :delivered"

I think the correct output would be:

let joined = Object.keys(mappings).join(); // string: ":0, :1, :2"