Basic URI parser in JS

parse-uri.js

// JS version of Python partition function
function partition(s, delimiter) {
    const i = s.indexOf(delimiter);
    if (i >= 0) return [s.substring(0, i), s[i], s.substring(i + 1)];
    else return [s, "", ""];
}

// JS version of Python rpartition function
function rpartition(s, delimiter) {
    const i = s.lastIndexOf(delimiter);
    if (i >= 0) return [s.substring(0, i), s[i], s.substring(i + 1)];
    else return ["", "", s];
}

// Parse an authority string into an object
// with the following keys:
// - userInfo (optional, might contain both user name and password)
// - host
// - port (optional, included only as a string)
function parseAuthority(value) {
    let parsed = {}, parts;
    
    // Parse user info
    parts = rpartition(value, "@");
    if (parts[1] === "@") {
        parsed.userInfo = decodeURIComponent(parts[0]);
        value = parts[2];
    }
    
    // Parse host and port
    parts = partition(value, ":");
    parsed.host = parts[0];
    if (parts[1] === ":") {
        parsed.port = parts[2];
    }
    
    return parsed;
}

// Parse a query string into an object. If repeated 
// keys exist, these will get overwritten.
function parseQueryString(value) {
    let parsed = {};
    value.split("&").forEach(function(bit) {
        let parts = partition(bit, "=");
        parsed[decodeURIComponent(parts[0])] = decodeURIComponent(parts[2]);
    });
    return parsed;
}

// Parse a URI into an object with the following 
// top-level keys:
// - scheme (optional)
// - authority (optional, further parsed if present)
// - path
// - query (optional, further parsed if present)
// - fragment (optional)
function parseURI(value) {
    let parsed = {}, parts;
  
    // Parse scheme
    parts = partition(value, ":");
    if (parts[1] === ":") {
        parsed.scheme = decodeURIComponent(parts[0]);
        value = parts[2];
    }
    
    // Parse fragment
    parts = partition(value, "#");
    if (parts[1] === "#") {
        parsed.fragment = decodeURIComponent(parts[2]);
        value = parts[0];
    }
    
    // Parse query
    parts = partition(value, "?");
    if (parts[1] === "?") {
        parsed.query = parseQuery(parts[2]);
        value = parts[0];
    }
    
    // Parse authority and path
    if (value.startsWith("//")) {
        parts = partition(value.substr(2), "/");
        parsed.authority = parseAuthority(parts[0]);
        parsed.path = parts[1] + parts[2];
    }
    else {
        parsed.path = value;
    }
    
    return parsed
}

// And here's how to use it
console.log(parseURI('neo4j+s://antonio@example.com:7687?region=brazil'));