JSFiddle - React, Tailwind, and code Playground

JavaScript

dataset=[];
dataset[0]=[{data:29, color:"y"},{data:44, color:"g"}]
dataset[1]=[{data:16, color:"r"},{data:23, color:"m"},{data:23, color:"b"}]

sum1=dataset[0].length
sum2=dataset[1].length

for(i=0;i<sum1;i++)
{
    dataset[1].unshift({data:0, color:null})
}

for(i=0;i<sum2;i++)
{
   dataset[0].splice(2, 0, {data:0, color:null});
}

console.log(dataset[0]);
console.log(dataset[1]);