diff --git a/javascript/index.js b/javascript/index.js
index d0fcca9..63510e2 100644
--- a/javascript/index.js
+++ b/javascript/index.js
@@ -25,7 +25,7 @@ const ELEVATION = 3;
 const CUSTOM1 = 6;
 const CUSTOM2 = 7;
 
-const Num = typeof BigInt !== "undefined" ? BigInt : Number;
+const Num = (typeof BigInt === "undefined" || (typeof process === "object" ? process : {}).env?.FORCE_NUMBER_TYPE) ? Number : BigInt; 
 
 function decode(encoded) {
     const decoder = decodeUnsignedValues(encoded);
@@ -77,11 +77,12 @@ function decodeUnsignedValues(encoded) {
     let result = Num(0);
     let shift = Num(0);
     const resList = [];
+    const mask = Num(0x20);
 
     encoded.split('').forEach((char) => {
         const value = Num(decodeChar(char));
-        result |= (value & Num(0x1F)) << shift;
-        if ((value & Num(0x20)) === Num(0)) {
+        result += (value % Num(32)) * (Num(2) ** shift);
+        if ((value % (mask * Num(2))) < mask) {
             resList.push(result);
             result = Num(0);
             shift = Num(0);
@@ -111,11 +112,11 @@ function decodeHeader(version, encodedHeader) {
 function toSigned(val) {
     // Decode the sign from an unsigned value
     let res = val;
-    if (res & Num(1)) {
-        res = ~res;
+    if (res % Num(2)) {
+        res = (res + Num(1)) * Num(-1);
     }
-    res >>= Num(1);
-    return +res.toString();
+    res = res / Num(2);
+    return Math.floor(+res.toString());
 }
 
 function encode({ precision = DEFAULT_PRECISION, thirdDim = ABSENT, thirdDimPrecision = 0, polyline }) {
@@ -171,10 +172,15 @@ function encodeUnsignedNumber(val) {
     // Uses variable integer encoding to encode an unsigned integer. Returns the encoded string.
     let res = '';
     let numVal = Num(val);
+    const bigIntSupported = typeof numVal === 'bigint';
     while (numVal > 0x1F) {
-        const pos = (numVal & Num(0x1F)) | Num(0x20);
+        const pos = (numVal % Num(32)) + Num(32);
         res += ENCODING_TABLE[pos];
-        numVal >>= Num(5);
+        if (bigIntSupported) {
+            numVal >>= Num(5);
+        } else {
+            numVal = parseInt(numVal / Num(32));
+        }
     }
     return res + ENCODING_TABLE[numVal];
 }
@@ -184,9 +190,9 @@ function encodeScaledValue(value) {
     //   `appender` is a callable where the produced chars will land to
     let numVal = Num(value);
     const negative = numVal < 0;
-    numVal <<= Num(1);
+    numVal = numVal * Num(2);
     if (negative) {
-        numVal = ~numVal;
+        numVal = numVal * Num(-1) - Num(1);
     }
 
     return encodeUnsignedNumber(numVal);
diff --git a/javascript/package.json b/javascript/package.json
index b4b366a..a18ce6e 100644
--- a/javascript/package.json
+++ b/javascript/package.json
@@ -6,7 +6,7 @@
   "types": "index.d.ts",
   "scripts": {
     "prepack": "cp ../LICENSE .",
-    "test": "node test/test.js",
+    "test": "node test/test.js && FORCE_NUMBER_TYPE=true node test/test.js",
     "release": "./release.sh"
   },
   "keywords": [