JSFiddle - React, Tailwind, and code Playground

HTML

<p id = 'y'>

</p>

JavaScript

var namaFile = [
    {
        billingID: "90009388",
        customerID: "C20121121221327_249",
        name: "201409011141106_082895250262"
    },
    {
        billingID: "90009400",
        customerID: "7885000000007804",
        name: "201410201141125_08287045931"
    },
    {
        billingID: "90009388",
        customerID: "C20121121221327_249",
        name: "201410011171208_082895250262"
    }
];

var emailAddr = [
    {
        customerID: "C20121121221327_249",
        email: "[email protected]"
    },
    {
        customerID: "7885000000007804",
        email: "[email protected]"
    }
];

for (var j = 0; j < emailAddr.length; j++) {
    var files = [];
    for (var i = 0; i < namaFile.length; i++) {
        if (namaFile[i].customerID == emailAddr[j].customerID) {
            files.push(namaFile[i].name);
            emailAddr[j]['files'] = files;
        }
    }
}

var message = document.getElementbyID('y');
message.innerHTML=emailAddr;