makesPairWith.js

/* makesPairWith returns a boolean indicating if the 
 * given array (inArr) contains a pair of numbers that 
 * add up to the target
 * 
 * inArr - The array to be flattened
 * target - The number the pairs may add up to
 */

function makesPairWith(inArr,target) {
    for (var i=0; i < inArr.length; i++) {
        var a = inArr[i];

        // Because we don't need [b,a] if we've already looked at 
        // [a,b] in a previous loop we can make the inner loop 
        // shorter with each cycle of the outer loop.
        for (var j=i+1; j < inArr.length; j++) {
            var b = inArr[j];
            if (a+b===target) {
                return true;
            }
        }
    }
    return false;
}



/* I'm provding a function here that tests/demonstrates the makesPairWith 
 * function above. Returns a boolean indicating the test pass status. */
function testMakesPairWith() {
  //tests is an array of objects, each with an input and an expected output
  //input itself is an array which is passed to the tested function with apply
    var tests = [{ 
        input : [ [1,2,3,4,5,6,7,8,9], 12],
        expected : true
    }, {
        input : [ [1,1,2], 2],
        expected : true
    }, {
        input : [ [1,1,1], 3],
        expected : false
    }, {
        input : [ [1,2,3,4,5,6], 20],
        expected : false
    }];

    var passed = true;
    tests.forEach(function(test, i) {
        if (makesPairWith.apply(undefined, test.input)===test.expected) {
            console.log("Test Passed:", i+1);
        } else {
            console.log("Test Failed:", i+1);
            passed = false;
        }
    });
    return passed;
  
}