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diff --git a/challenge-002/zapwai/javascript/ch-2.js b/challenge-002/zapwai/javascript/ch-2.js
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+const alph = "0123456789abcdefghijklmnopqrstuvwxy";
+
+// input a base-35 number (a string), output base-10
+const from35 = function(s) {
+    let n = s.length - 1;
+    let sum = 0;
+    for (let d of s) {
+	sum += alph.indexOf(d) * Math.pow(35,n);
+	n--;
+    }
+    return sum;
+};
+
+// input base-10, output base-35
+const to35 = function(d) {
+    let rem = parseInt(d % "35");
+    let n = 0;
+    while (true) {
+	let q = parseInt(d / String(Math.pow(35, n+1)));
+	if ( q < 1 ) {
+	    break;
+	}
+	n++;
+    }
+    let coeffs = [];
+    for (let k = n; k > 0; k--) {
+	coeffs.push( Math.floor(d / Math.pow(35, k)) );
+    }
+    coeffs.push(rem);
+
+    let s = "";
+    for (let c of coeffs) {
+	s += alph.charAt(c);
+    }
+    return s;
+};
+
+// 2u <- 2(35) + 30 = 100
+let num = "1000";
+console.log("Input: (base-10) ", num);
+console.log("Output: (base-35) ", to35(num));
+// 120 = 105 + 15 -> 3(35) + 15
+let x = "3f";
+console.log("Input: (base-35) ", x);
+console.log("Output: (base-10)", from35(x));
+
+// // // // // // // // // // // // 
+//  Proper way (would work for bases up to 36):
+
+// function to35(d) {
+//     return d.toString(35);
+// }
+
+// function to10(s) {
+//     return parseInt(s, 35);
+// }
+
+// example
+// let d = 100;
+// let x = d.toString(35);		// a base-35 number
+// console.log(x);			// 2u
+// console.log(parseInt(x, 35));	// 100   base-35 -> base-10
+