Javascript JSON syntax highlight

json-syntax-highlighter.js

    const isISODate = date => new Date(date) !== "Invalid Date" && !isNaN(new Date(date)) && date == new Date(date).toISOString();

    const syntaxHighlight = json => {
        json = JSON.stringify(json, null, '   ')
        json = json.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
        var result = json.replace(/("(\\u[a-zA-Z0-9]{4}|\\[^u]|[^\\"])*"(\s*:)?|\b(true|false|null)\b|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?)/g, function (match) {
            var cls = '';
            if (/^"/.test(match)) {
                if (/:$/.test(match)) {
                    cls = 'key';
                    match = match.substring(1, match.length-2);
                } else {
                    if (/"[\d]+"/.test(match)) cls = 'number';
                    else cls = 'string';
                    match = match.substring(1, match.length-1);
                    if(isISODate(match)) cls = 'date';
                }
            } else if (/true|false/.test(match)) {
                cls = 'boolean';
            } else if (/null/.test(match)) {
                cls = 'null';
            }
            if (cls === 'key') return '<span class="' + cls + '">' + match + '</span>:';
            else if (cls === 'string') return '"<span class="' + cls + '">' + match + '</span>"';
            else return '<span class="' + cls + '">' + match + '</span>';
        });
        return result;
    }

style.css

.key {
    color:#ddd;
}
.string {
    color:rgb(46, 204, 113);
}
.number {
    color:lightblue;
}
.boolean {
    color:yellow;
}
.date {
    color:Brown;
}
.null {
    color:gray;
}
.version {
    color:blue;
}


.container {
    color: gray;
    white-space:pre;
    user-select:text;
    -webkit-user-select:text;
    font-family:DejavuSans;
}