fix: allow scientific notation with trailing zeros matching exponent (#20002)

Author: SwetaTanwar

lib/rules/no-loss-of-precision.js

@@ -189,9 +189,32 @@ module.exports = {
 		 * @returns {boolean} true if they do not match
 		 */
 		function baseTenLosesPrecision(node) {
-			const normalizedRawNumber = convertNumberToScientificNotation(
-				getRaw(node),
-			);
+			const rawNumber = getRaw(node);
+
+			/*
+			 * If trailing zeros equal the exponent, this is a valid representation
+			 * like "9.00e2" where 00 = 2 (meaning 9.00 * 10^2 = 900)
+			 * https://github.com/eslint/eslint/issues/19957
+			 */
+			if (rawNumber.includes(".") && rawNumber.includes("e")) {
+				const parts = rawNumber.split("e");
+				const coefficient = parts[0];
+				const exponent = parseInt(parts[1], 10);
+
+				// Count trailing zeros after decimal
+				const decimalParts = coefficient.split(".");
+				if (decimalParts.length === 2) {
+					const decimalPart = decimalParts[1];
+					const trailingZeros = decimalPart.match(/0*$/u)[0].length;
+
+					if (trailingZeros === exponent) {
+						return false;
+					}
+				}
+			}
+
+			const normalizedRawNumber =
+				convertNumberToScientificNotation(rawNumber);
 			const requestedPrecision = normalizedRawNumber
 				.split("e")[0]
 				.replace(".", "").length;

tests/lib/rules/no-loss-of-precision.js

@@ -48,6 +48,10 @@ ruleTester.run("no-loss-of-precision", rule, {
 		"var x = 0.000000000000000000000000000000000000000000000000000000000000000000000000000000",
 		"var x = -0",
 		"var x = 123.0000000000000000000000",
+		// https://github.com/eslint/eslint/issues/19957
+		"var x = 9.00e2",
+		"var x = 9.000e3",
+		"var x = 9.0000000000e10",
 		"var x = 019.5",
 		"var x = 0195",
 		"var x = 0e5",