Javascript to compare different software version strings (ex: 1.0.4 vs 1.1.4). Can handle pre, beta, etc prefixes/suffixes.

version_compare.js

// Some versions to test [v1, v2, expected result]
var versions = [
    ['1.2.0', '1.2', 0],
    ['1.4', '1.7.2', 1],
    ['1.2pre', '1.2', 1],
    ['1.7', '1.1.1', -1],
    ['1.7.9RC1', '1.7.9RC2', 1],
    ['1.7.9RC1', '1.7.9RC', -1],   
    ['1.7.9RC1', '1.7.9', 1],       
    ['0.4beta', '0.4', 1],
    ['0.4beta', '0.4alpha', -1],    
    ['0.4b', '0.4b', 0],     
    ['0.0.1', '0.0.0.1', -1],        
];    

// Compare test versions
for (var i = 0; i < versions.length; ++i) {
    var a = versions[i][0], 
        b = versions[i][1],
        e = versions[i][2],
        c = version_compare(a, b);                     
    
    document.write(a + ' <-> ' + b + ' = ' + c + ' ' + (e === c) + '<br>');
}
    
/*
Split a version string into components and map prefixes and suffixes to integers.

Examples:
- 1.0
- 2.0.4
- 1.4RC
- 0.7beta
*/
function version_bits(version) {
    version = version.replace(/(\d+)([^\d\.]+)/, '$1.$2');
    version = version.replace(/([^\d\.]+)(\d+)/, '$1.$2');    
    var parts = version.split('.'), 
        rmap = {
            'rc' : -1,
            'pre' : -2,            
            'beta' : -3,
            'b' : -3,            
            'alpha' : -4,
            'a' : -4,            
        },
        v, n;
    
    var bits = [];
    for (var i = 0; i < parts.length; ++i) {
        v = parts[i];
            
        n = parseInt(v, 10);
        if ( isNaN(n) ) {
            n = rmap[v] || -1;
        }
        bits.push(n);
    }    
    return bits;
}

/*
Compare different software version strings.

Returns 0 if same, -1 if version2 is older or 1 if version2 is newer.
*/
function version_compare(version1, version2) {
    var v1parts = version_bits(version1);
    var v2parts = version_bits(version2);
    var v2, v1;
    
    for (var i = 0; i < Math.max(v1parts.length, v2parts.length); ++i) {
        v1 = v1parts[i] || 0;
        v2 = v2parts[i] || 0;
        
        if (v2 > v1) {
            return 1;
        }
        else if (v1 > v2) {
            return -1;
        }
    }
        
    return 0;
}​