JavaScript constants

<script type="text/javascript">
    /**
     * This is one way to do constants in JS
     * Constants are usually UPPERCASE but I put a fail-safe in to accept UPPER, lower and MixED cASe
     * Also did a parseFloat on the return, which may not strictly be necessary - MMXIV Donkeysoft
     */
    function constants(type) {
        _c = [];
    _c["ft"] = 0.3048;
    _c["pi"] = 3.1415;
        return parseFloat( _c[ type.toLowerCase() ] )
    }
    console.log( "There are exactly " + constants("FT") + "metres to the foot" );
    console.log( "The value of PI is exactly " + constants("PI") );
</script>