JSFiddle - React, Tailwind, and code Playground

JavaScript

var html ="";
		var str = "1";
		var matrixSide = 31;
		var rowCount = 0;
		var appendPrependStr = "";
		var back = false;

		for ( i = 0; i < ((matrixSide - str.length) / 2); i++) {
			appendPrependStr += "0";
		}

		while (true) {
			rowCount++;
            html+= appendPrependStr + str + appendPrependStr + "<br>";
			if (rowCount == matrixSide) {
				break;
			}
			if (back) {
				str = str.substring(2);
				appendPrependStr += 0;
			} else {
				str += "11";
				appendPrependStr = appendPrependStr.substring(1);
			}
			if (str.length >= matrixSide) {
				back = !back;
			}
		}
        document.body.innerHTML = html;