4_5. Vector Math

function main(){
    function add(v1,v2){
        let r=[v1[0] + v2[0], v1[1] + v2[1]];
          return r;
    }

    function multiply(v1,v2){
        let r=[v1[0]*v2, v1[1]*v2];
          return r;
    }

    function length(v1){
        let r=Math.sqrt((v1[0]*v1[0])+(v1[1]*v1[1]));
         return r;
    }

    function dot(v1,v2){
        let r=(v1[0]*v1[1])+(v2[0]*v2[1]);
        return r;
    }

    function cross(v1,v2){
        let r=(v1[0]*v2[1])-(v1[1]*v2[0]);
         return r;
    }

    return{add, multiply, length, dot, cross}
}

let result=main();

console.log(result.add([1, 1], [1, 0]));
console.log(result.multiply([3.5, -2], 2));
console.log(result.length([3, -4]));
console.log(result.dot([1, 0], [0, -1]));
console.log(result.cross([3, 7], [1, 0]));