Accepted v1

var matrixReshape = function(nums, r, c) {
    var or = nums.length;
    var matrixFull = new Array();
    var matrixNew = new Array();
        for (var i=0;i<or;i++){
            matrixFull = matrixFull.concat(nums[i]);
        };
        if (r*c != matrixFull.length){
            return nums;
        } else {
            for (var i=0;i<r;i++){
                matrixNew[i] = matrixFull.slice(i*c,i*c+c);
            }
            return matrixNew;
        }
};

For Test

var matrixReshape = function(nums, r, c) {
    var or = nums.length;
    var matrixFull = new Array();
    var matrixNew = new Array();
        for (var i=0;i<or;i++){
            matrixFull = matrixFull.concat(nums[i]);
            console.log(matrixFull);
        };
        if (r*c != matrixFull.length){
            return nums;
            console.log("WRONG !!!");
        } else {
            for (var i=0;i<r;i++){
                matrixNew[i] = matrixFull.slice(i*c,i*c+c);
                console.log(matrixNew[i]);
            }
            return matrixNew;
        }
};

nums = [[1,2],[3,4],[5,6]];
r=6;
c=1;
matrixReshape(nums, r, c);