JavaScript构建字符串金字塔

//从侧面看金字塔
		function watchPyramidFromTheSide(characters) {
			var str = "";
			for(var i=characters.length-1;i>=0;i--){
				for(var j=0;j<i;j++){
					str += " ";
				}
				var num = 2 * characters.length - 1 - j * 2;
				for(j=0;j<num;j++){
					str += characters.charAt(i);
				}
				for(j=0;j<i;j++){
					str += " ";
				}
				if(i>0){
					str += "\n";
				}
			}
			return str;
		}
		
		//从上方看金字塔
		function watchPyramidFromAbove(characters) {
			var matrix = [];
			var str = "";
			//边最长为
			var sideLongest = characters.length * 2 - 1;
			for(var i=0;i<characters.length;i++){
				var chr = characters.charAt(i);
				for(var j=i;j<sideLongest-i;j++){
					if(!matrix[j]){
						matrix[j] = new Array(sideLongest);
					}
					for(var k=i;k<sideLongest-i;k++){
						matrix[j][k] = chr;
					}
				}
			}
			//组合字符串
			for(i=0;i<matrix.length;i++){
				str += matrix[i].join("");
				if(i<matrix.length-1){
					str += "\n";
				}
			}
			return str;
		}
		
		//能看到的金字塔字符数
		function countVisibleCharactersOfThePyramid(characters) {
			return Math.pow(characters.length * 2 - 1,2);
		}
		
		//金字塔总字符数
		function countAllCharactersOfThePyramid(characters) {
			var len = characters.length;
			var count = 0;
			while(len >= 1){
				count += Math.pow(2 * len - 1,2);
				len--;
			}
			return count;
		}