Question

Does anyone have code to compare two version numbers in JavaScript? I just want simple version comparisons (e.g. "1.0" vs "1.5.6"), and it should work with numbers or strings. It can ignore trailing beta identifiers like "1.5.6b4", but can otherwise expect the strings to be well-formed. The function should return a signed integer like a normal cmp function.

function cmpVersion(a, b)
  return less than one if a < b
  return 0 if a == b
  return greater than one if a > b

I have an answer, but will choose a better or more elegant solution over my own.

(I am using this to compare jQuery.browser.version numbers, but the answer will be more widely applicable)

Answer 1

function cmpVersion(a, b) {
    var i, cmp, len;
    a = (a + '').split('.');
    b = (b + '').split('.');
    len = Math.max(a.length, b.length);
    for( i = 0; i < len; i++ ) {
        if( a[i] === undefined ) {
            a[i] = '0';
        }
        if( b[i] === undefined ) {
            b[i] = '0';
        }
        cmp = parseInt(a[i], 10) - parseInt(b[i], 10);
        if( cmp !== 0 ) {
            return (cmp < 0 ? -1 : 1);
        }
    }
    return 0;
}

function gteVersion(a, b) {
    return cmpVersion(a, b) >= 0;
}
function ltVersion(a, b) {
    return cmpVersion(a, b) < 0;
}

This function handles:

• numbers or strings as input
• trailing zeros (e.g. cmpVersion("1.0", 1) returns 0)
• ignores trailing alpha, b, pre4, etc