[TSC-9] Add numeric input validator module

- Create validator.js with validateNumericInput() function - Validates numeric strings; allows digits, leading minus, single decimal point - Rejects invalid characters, multiple decimals, misplaced minus signs - Returns { isValid, value, sanitized } object - Link validator.js in index.html <head> - Update CLAUDE.md project structure to include validator.js
2026-07-08 07:58:12 +00:00
3 changed files with 49 additions and 0 deletions
--- a/CLAUDE.md
+++ b/CLAUDE.md
@ -8,6 +8,7 @@ Greenfield project. Implementation is driven by the Vexa AI-SDLC pipeline (Jira
 /
 ├── index.html  # Calculator UI (semantic HTML5)
 ├── styles.css  # Responsive CSS layout and styling
+├── validator.js  # Numeric input validator (validateNumericInput)
 ├── README.md   # Project overview
 └── CLAUDE.md   # This file
 ```
--- a/index.html
+++ b/index.html
@ -5,6 +5,7 @@
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Simple Calculator</title>
  <link rel="stylesheet" href="styles.css">
+  <script src="validator.js"></script>
 </head>
 <body>
  <main>
--- a/validator.js
+++ b/validator.js
@ -0,0 +1,47 @@
+/**
+ * Validates a numeric input string.
+ *
+ * Allowed characters: digits 0-9, a single decimal point, a leading minus sign.
+ * Returns an object with:
+ *   isValid  {boolean} - true when the string represents a well-formed number
+ *   value    {number|null} - parsed numeric value, or null when invalid
+ *   sanitized {string} - trimmed input string
+ */
+function validateNumericInput(input) {
+  var str = String(input).trim();
+  var result = { isValid: false, value: null, sanitized: str };
+
+  if (str === '') {
+    return result;
+  }
+
+  // Reject characters other than digits, decimal point, and minus sign
+  if (/[^0-9.\-]/.test(str)) {
+    return result;
+  }
+
+  // Minus sign is only valid as the very first character
+  var minusCount = (str.match(/-/g) || []).length;
+  if (minusCount > 1 || (minusCount === 1 && str.charAt(0) !== '-')) {
+    return result;
+  }
+
+  // Only one decimal point is allowed
+  if ((str.match(/\./g) || []).length > 1) {
+    return result;
+  }
+
+  // A bare '-' or '.' is not a valid number
+  if (str === '-' || str === '.') {
+    return result;
+  }
+
+  var parsed = parseFloat(str);
+  if (isNaN(parsed)) {
+    return result;
+  }
+
+  result.isValid = true;
+  result.value = parsed;
+  return result;
+}