JSFiddle - React, Tailwind, and code Playground

CSS

rect[foo] {
    fill: red;
}

rect[myns\:foo] {
    fill: green;
}

JavaScript

d3.select("body")
    .append("svg")
    .attr({width: 100, height: 100})
    .append("rect")
        .attr({width: 100, height: 100})
        .attr("myns:foo", "bar");