var val = null;
if (period.indexOf('Jan') !== -1) {
    val = 1;
} else if (period.indexOf('Feb') !== -1) {
    val = 2;
} else if (period.indexOf('Mar') !== -1) {
    val = 3;
} else if (period.indexOf('Apr') !== -1) {
    val = 4;
} else if (period.indexOf('May') !== -1) {
    val = 5;
} else if (period.indexOf('Jun') !== -1) {
    val = 6;
} else if (period.indexOf('Jul') !== -1) {
    val = 7;
} else if (period.indexOf('Aug') !== -1) {
    val = 8;
} else if (period.indexOf('Sep') !== -1) {
    val = 9;
} else if (period.indexOf('Oct') !== -1) {
    val = 10;
} else if (period.indexOf('Nov') !== -1) {
    val = 11;
} else if (period.indexOf('Dec') !== -1) {
    val = 12;
} else {
    val = -1;
}

I have a strong feeling there's a better way to do this, but it's not coming to me. I've used json object dictionaries for similar routing logic, but it doesn't seem to apply in this case.