fix: fromWei() parsing of large numbers > 10^20

packages/web3-utils/CHANGELOG.md

@@ -199,4 +199,9 @@ Documentation:
 
 -   replaced our eventEmitter to EventEmitter3 to support react native builds (#6253)
 
-## [Unreleased]
+## [Unreleased]
+
+### Fixed
+
+- fixed erroneous parsing of big numbers in the `fromWei(...)` function (#6880)
+

packages/web3-utils/src/converters.ts

@@ -411,6 +411,13 @@ export const toHex = (
  */
 export const toNumber = (value: Numbers): number | bigint => {
 	if (typeof value === 'number') {
+            if (value > 1e+20) {
+                // JavaScript converts numbers >= 10^21 to scientific notation when coerced to strings,
+                // leading to potential parsing errors and incorrect representations.
+                // For instance, String(10000000000000000000000) yields '1e+22'.
+                // Using BigInt prevents this
+                return BigInt(value);
+            }
 		return value;
 	}
 

packages/web3-utils/test/fixtures/converters.ts

@@ -279,7 +279,10 @@ const conversionBaseData: [[Numbers, EtherUnits], string][] = [
 
 export const fromWeiValidData: [[Numbers, EtherUnits], string][] = [
 	...conversionBaseData,
-	[['0xff', 'wei'], '255'],
+    [['0xff', 'wei'], '255'],
+    [[1e+22, 'ether'], '10000'],
+    [[19999999999999991611392, 'ether'], '19999.999999999991611392'],
+    [[1.9999999999999991611392e+22, 'ether'], '19999.999999999991611392'],
 ];
 
 export const toWeiValidData: [[Numbers, EtherUnits], string][] = [