queryStringToObject

query_string_to_object.js

// Read query string parameters as a javascript object.
//
// Not tested for:
//
// * Mixing bracketed and non-bracketed keys
// * Indexed brackets
// * Nested lists
//
// Some examples (See unit tests below for full details):
//
// | query string |       result       |
// |--------------|--------------------|
// | undefined    | uses current URL   |
// | ?            | {}                 |
// | ?a           | {a: undefined}     |
// | ?a=          | {a: undefined}     |
// | ?a=1&b=2     | {a: 1, b: 2}       |
// | a=1&b=2      | {a: 1, b: 2}       |
// | ?a[]=1&b=2   | {a: [1], b: 2}     |
// | ?a=1&a=2     | {a: [1, 2]}        |
// | ?a[]=1&a[]=2 | {a: [1, 2]}        |
// | ?a[]=1&a=2   | undefined behavior |
// | ?a[1]=1      | undefined behavior |
// | ?a[][]=1     | undefined behavior |

var queryStringToObject = function (queryString) {
    var params = {};
    // Allow for easy invocation in the default case.
    if (queryString === undefined) {
        queryString = window.location.search;
    }
    // Leading question mark optional.
    if (queryString.charAt(0) === '?') {
        queryString = queryString.substring(1);
    }
    // Quick return for empty query string.
    if (queryString === '') {
        return params;
    }
    // Separate the query string into key-value pairs.
    // Be careful with split! ''.split('&') gets you ['']
    var pairStrings = queryString.indexOf('&') === -1 ?
        [queryString] : queryString.split('&');
    // Add each key-value pair to the params object.
    pairStrings.forEach(function (pairStr) {
        // Split up the key and value, decoding URL escaping.
        var pair = pairStr.split('='),
                key = decodeURIComponent(pair[0]),
                value = pair[1] ? decodeURIComponent(pair[1]) : undefined,
                // A key becomes a list if either 1) it repeats or 2) it ends in [].
                keyIsList = false;
        // Check for bracket notation.
        if (key.substr(-2) === '[]') {
            keyIsList = true;
            key = key.substr(0, key.length - 2);
        }
        // Check for repeats.
        if (key in params && !(params[key] instanceof Array)) {
            keyIsList = true;
            params[key] = [params[key]];
        }
        // Lists keys need to be pushed, not assigned.
        if (keyIsList) {
            // Never-before-seen bracketed keys need their list initialized.
            if (!(key in params)) {
                params[key] = [];
            }
            // Pushing undefined does "set" that index in the array. It's cleaner
            // to not push it if the key has no value.
            if (value !== undefined) {
                params[key].push(value);
            }
        } else {
            // Simple assignment for non-list keys.
            params[key] = value;
        }
    });
    return params;
};

// Query string unit tests. Returns map of test names to success true/false.
(function (f) {
    var tests = [
        function normalNonRepeated() {
            var p = f('?foo=bar&baz=quz');
            return p.foo === 'bar' && p.baz === 'quz';
        },
        function normalNonRepeatedWithoutQuestionMark() {
            var p = f('foo=bar&baz=quz');
            return p.foo === 'bar' && p.baz === 'quz';
        },
        function empty() {
            var p = f('?');
            return p !== null && p !== undefined && p.constructor === Object;
        },
        function valuelessWithEquals() {
            var p = f('?foo=&baz=quz');
            return p.foo === undefined && p.baz === 'quz';
        },
        function valuelessWithEqualsSimple() {
            var p = f('?foo=');
            return p.foo === undefined;
        },
        function valuelessWithoutEquals() {
            var p = f('?foo&baz=quz');
            return p.foo === undefined && p.baz === 'quz';
        },
        function valuelessWithoutEqualsSimple() {
            var p = f('?foo');
            return p.foo === undefined;
        },
        function repeatedWithoutBrackets() {
            var p = f('?foo=bar1&foo=bar2&baz=quz');
            return p.foo[0] === 'bar1' && p.foo[1] === 'bar2' && p.baz === 'quz';
        },
        function repeatedWithBrackets() {
            var p = f('?foo[]=bar1&foo[]=bar2&baz=quz');
            return p.foo[0] === 'bar1' && p.foo[1] === 'bar2' && p.baz === 'quz';
        },
        function decodesUrlComponents() {
            var p = f('?%E3%81%BB%E3%81%92=%E3%81%BB%E3%81%92');
            return p['ほげ'] === 'ほげ';
        }
    ];
    var results = {};
    tests.forEach(function (testFn) {
        var success = false;
        try {
            success = testFn();
        } catch (e) {}
        results[testFn.name] = success;
        if (!success) {
            console.error("Unit testfailed:", testFn.name);
        }
    });
    return results;
}(queryStringToObject));