spiral-matrix.js

/**
 * @param {number[][]} matrix
 * @return {number[]}
 */

var spiralOrder = function(matrix) {

    if(!matrix.length || !matrix[0].length){
			return [];
	}
    
	//Use 4 pointes to create wall around square
	
    let rowBegin = 0,
	    rowEnd = matrix.length - 1,
	    colBegin = 0,
	    colEnd = matrix[0].length - 1;

	let result = [];
	while(rowBegin <= rowEnd && colBegin <= colEnd){

		//move right
		
        for(let i= colBegin; i<= colEnd; i++){
				result.push(matrix[rowBegin][i]);
		}
		rowBegin++; // mark row as traversed after moving right

		//move down
		
        for(let i=rowBegin; i<= rowEnd; i++){
				result.push(matrix[i][colEnd]);
		}
		colEnd--; //mark column as traversed after moving down

		//move left
		
        if(rowBegin <= rowEnd){
				for(let i=colEnd; i >= colBegin; i--){
						result.push(matrix[rowEnd][i]); 
				}
		}
		rowEnd--; //mark end row as traversed after moving left

		//move up
		
        if(colBegin <= colEnd){ 
				for(let i=rowEnd; i >= rowBegin; i--){
						result.push(matrix[i][colBegin]);
				}
		}
		colBegin++; //mark begining column as traversed after moving up
	}

	return result;
    
};