JSFiddle - React, Tailwind, and code Playground

HTML

<body id="myText">
<span></span>
</body>

JavaScript

var data = '<abc name = "foo">\n<child>bar</child>\n</abc>\n<xyz>1</xyz>\n<abc name = "foo2">\n<child>bar2</child>\n</abc>\n<xyz>5</xyz>';

var regexapi = /<\/abc>\n(?:<xyz>(.*)(?=<\/xyz))*/gim;
var array1 = [];
while ( (resApi = regexapi.exec(data))) {
    array1.push(resApi[0]);
}

document.getElementById("myText").innerHTML = array1[0];