JSFiddle - React, Tailwind, and code Playground

JavaScript

var multi = [
    ["a","b","c"],
    ["d","e","f"],
    ["g","h","i"],
]
var multi2 = [];

for (var i = 0; i < multi.length; i++) { // 2
    for (var j = 0; j < multi[i].length; j++) { // 3
        multi2[j] = multi2[j]||[];
        multi2[j].push(multi[i][j])
    }
}
console.warn(multi2);