Find pairs that equal 100, remove duplicate pairs.

gistfile1.txt

Array.prototype.sumPairs = function(){
    var arr = this, pairs = [], subPair, currentElem, compareElem;

    for(var i = 0; i < arr.length; i++){
      currentElem = arr[i];
    	for(var j = i+1; j<arr.length; j++){
    		compareElem = arr[j];
    		if((currentElem + compareElem) === 100){
    			subPair = new Array();
    			subPair.push(currentElem);
    			subPair.push(compareElem);
    			pairs.push(subPair.sort());
    		}
    	}
    }
    return uniqPairs(pairs);
}

function uniqPairs(arr) {
    var seen = {};
    return arr.filter(function(elem) {
        var k = JSON.stringify(elem);
        return (seen[k] === 1) ? 0 : seen[k] = 1;
    })
}

console.log([1,98,99].sumPairs());
console.log([95,5,95].sumPairs());
console.log([95,5,95,5].sumPairs());
console.log([80,5,20,25,75,15,2,5,2,85].sumPairs());