Sequelize how to insert update multiple rows?

Question

I am trying to insert multiple rows into my database using Sequelize, but the for loop is stuck due to some violation of restrictions.

        let dataset = [
             ["2016-01-01","987"],
             ["2016-01-02","987"],
             ["2016-01-03","987"],
             ["2016-01-04","987"],
             ["2016-01-05","987"],
             ["2016-01-06","987"],
             ["2016-01-07","987"],
             ...
        ];
        for(let row of dataset) {       
            model.findOrCreate({
                where: {date_prc: row[0]},
                defaults: {value: row[1]}
            });
        }

When I look at the SQL log, it checks to see if the date has already been inserted, and if it is not trying to insert a row. But in some cases, instead of inserting the missing date string, it inserts the next date.

For example, in the log I see:

 select 2016-01-03 // this one is missing
 select 2016-01-04 // this one is not missing
 insert 2016-01-04 // it is inserting 2016-01-04 instead of 2016-01-03