Pass data from an HTML script tag to JavaScript

script-data.js

const JSON_RE = /^(?:\{[\w\W]*\}|\[[\w\W]*\])$/;

function parseData(data) {
    if (data == null || data === 'null' || data === 'undefined' || data === '') {
        return null;
    }
    if (data === 'true') {
        return true;
    }
    if (data === 'false') {
        return false;
    }
    if (data === +data + '') {
        return +data;
    }
    if (JSON_RE.test(data)) {
        try {
            return JSON.parse(data);
        } catch(e) {}
    }
    return data;
}

function getScriptData(script = document.currentScript) {
    const data = {};
    for (let name in script.dataset) {
        data[name] = parseData(script.dataset[name]);
    }
    return data;
}

script-example.html

<script data-foo="Hello World", data-bar="true" data-baz="14.5" data-qux="{&quot;foo&quot;:&quot;bar&quot;}">

const data = getScriptData();
data.foo; //=> "Hello World"
data.bar; //=> true
data.baz; //=> 14.5
data.qux; //=> {foo: "bar"}

</script>