JSFiddle - React, Tailwind, and code Playground

JavaScript

var arr = [{"a1" : "a1Val", "a2" : "a2Val", "a3" : "a3Val"}, 
    {"b1" : "b1Val", "b2" : "b2Val", "b3" : "b3Val"},
    {"z1" : "z1Val", "z2" : "z2Val", "z3" : "z3Val"}];

var result = arr
    .map(function (obj) { 
        return Object.keys(obj).map(function (key) {
            var result = {};
            result[key] = obj[key];
            
            if (key.substring(1) === "2") {
                return result;
            }
        });
    })
    .reduce(function (x, y) { return x.concat(y); }, [])
    .filter(function (obj) { return obj })

console.log(result);