var

map = {},

precedence = [],

highestPrecedenceFound = precedence.length,

i,j,insensitiveSource;

if (source !== undefined && source !== null) {

// look through each source value

for (i=0;i<source.length;i++) {

insensitiveSource = source[i].toLowerCase().replace(/\s*(^|$|,|=)\s*/g, "$1");

// if we have a (case-and-whitespace insensitive) match in our map for this source

if (map[insensitiveSource]) {

// see if there is a higher-precedence entry available

// than whatever we already might have

for (j=0;j<highestPrecedenceFound;j++) {

if (precedence[j] === map[insensitiveSource]) {

// we found a higher precedence entry!

highestPrecedenceFound = j;

break;

}

}

}

}

}

precedence[highestPrecedenceFound] || null;