fix: preserve numeric precision and leading zeros

README.md

@@ -221,13 +221,49 @@ If the header is not on the first line you can define the header index like:
 Empty rows are ignored and not parsed.
 
 #### Format property value by type
-If you want that a number will be printed as a Number type, and values *true* or *false* is printed as a boolean Type, use:
+The `formatValueByType()` function intelligently converts string values to their appropriate types while preserving data integrity. To enable automatic type conversion:
+
 ```js
- csvToJson.formatValueByType()
-            .getJsonFromCsv(fileInputName);
+csvToJson.formatValueByType()
+         .getJsonFromCsv(fileInputName);
+```
+
+This conversion follows these rules:
+
+##### Numbers
+- Regular integers and decimals are converted to Number type
+- Numbers with leading zeros are preserved as strings (e.g., "0012" stays "0012")
+- Large integers outside JavaScript's safe range are preserved as strings
+- Valid decimal numbers are converted to Number type
+
+For example:
+```json
+{
+  "normalInteger": 42,           // Converted to number
+  "decimal": 3.14,              // Converted to number
+  "leadingZeros": "0012345",    // Kept as string to preserve leading zeros
+  "largeNumber": "9007199254740992"  // Kept as string to preserve precision
+}
+```
+
+##### Boolean
+Case-insensitive "true" or "false" strings are converted to boolean values:
+```json
+{
+  "registered": true,     // From "true" or "TRUE" or "True"
+  "active": false        // From "false" or "FALSE" or "False"
+}
+```
+
+##### Complete Example
+Input CSV:
+```csv
+first_name;last_name;email;gender;age;id;zip;registered
+Constantin;Langsdon;[email protected];Male;96;00123;123;true
+Norah;Raison;[email protected];Female;32;987;00456;FALSE
 ```
-For example: 
 
+Output JSON:
 ```json
 [
  {
@@ -236,38 +272,22 @@ For example:
   "email": "[email protected]",
   "gender": "Male",
   "age": 96,
-  "zip": 123,
-  "registered": true
+  "id": "00123",        // Preserved leading zeros
+  "zip": 123,          // Converted to number
+  "registered": true   // Converted to boolean
  },
  {
   "first_name": "Norah",
   "last_name": "Raison",
   "email": "[email protected]",
   "gender": "Female",
   "age": 32,
-  "zip": "",
-  "registered": false
+  "id": "987",
+  "zip": "00456",      // Preserved leading zeros
+  "registered": false  // Case-insensitive boolean conversion
  }
 ]
 ```
-##### Number
-The property **age** is printed as 
-```json
- "age": 32
-```
-instead of
-```json
-  "age": "32"
- ```
-##### Boolean
-The property **registered** is printed as 
-```json
- "registered": true
-```
-instead of
-```json
-  "registered": "true"
- ```
 
 #### Encoding
 You can read and decode files with the following encoding:

src/util/stringUtils.js

@@ -1,40 +1,109 @@
 'use strict';
 
 class StringUtils {
+    // Regular expressions as constants for better maintainability
+    static PATTERNS = {
+        INTEGER: /^-?\d+$/,
+        FLOAT: /^-?\d*\.\d+$/,
+        WHITESPACE: /\s/g
+    };
 
-    trimPropertyName(isTrimHeaderFieldWhiteSpace,value) {
-        if(isTrimHeaderFieldWhiteSpace) {
-            return value.replace(/\s/g, '');
+    static BOOLEAN_VALUES = {
+        TRUE: 'true',
+        FALSE: 'false'
+    };
+
+    /**
+     * Removes whitespace from property names based on configuration
+     * @param {boolean} shouldTrimAll - If true, removes all whitespace, otherwise only trims edges
+     * @param {string} propertyName - The property name to process
+     * @returns {string} The processed property name
+     */
+    trimPropertyName(shouldTrimAll, propertyName) {
+        if (!propertyName) {
+            return '';
         }
-        return value.trim();
-
+        return shouldTrimAll ? 
+            propertyName.replace(StringUtils.PATTERNS.WHITESPACE, '') : 
+            propertyName.trim();
     }
 
+    /**
+     * Converts a string value to its appropriate type while preserving data integrity
+     * @param {string} value - The input value to convert
+     * @returns {string|number|boolean} The converted value
+     */
     getValueFormatByType(value) {
-        if(value === undefined || value === ''){
+        if (this.isEmpty(value)) {
             return String();
         }
-        //is Number
-        let isNumber = !isNaN(value);
-        if (isNumber) {
-            return Number(value);
+
+        if (this.isBoolean(value)) {
+            return this.convertToBoolean(value);
+        }
+
+        if (this.isInteger(value)) {
+            return this.convertInteger(value);
         }
-        // is Boolean
-        if(value === "true" || value === "false"){
-            return JSON.parse(value.toLowerCase());
+
+        if (this.isFloat(value)) {
+            return this.convertFloat(value);
         }
+
         return String(value);
     }
 
-    hasContent(values) {
-        if (values.length > 0) {
-            for (let i = 0; i < values.length; i++) {
-                if (values[i]) {
-                    return true;
-                }
-            }
+    /**
+     * Checks if a value array contains any non-empty values
+     * @param {Array} values - Array to check for content
+     * @returns {boolean} True if array has any non-empty values
+     */
+    hasContent(values = []) {
+        return Array.isArray(values) && 
+               values.some(value => Boolean(value));
+    }
+
+    // Private helper methods for type checking and conversion
+    isEmpty(value) {
+        return value === undefined || value === '';
+    }
+
+    isBoolean(value) {
+        const normalizedValue = value.toLowerCase();
+        return normalizedValue === StringUtils.BOOLEAN_VALUES.TRUE || 
+               normalizedValue === StringUtils.BOOLEAN_VALUES.FALSE;
+    }
+
+    isInteger(value) {
+        return StringUtils.PATTERNS.INTEGER.test(value);
+    }
+
+    isFloat(value) {
+        return StringUtils.PATTERNS.FLOAT.test(value);
+    }
+
+    hasLeadingZero(value) {
+        const isPositiveWithLeadingZero = value.length > 1 && value[0] === '0';
+        const isNegativeWithLeadingZero = value.length > 2 && value[0] === '-' && value[1] === '0';
+        return isPositiveWithLeadingZero || isNegativeWithLeadingZero;
+    }
+
+    convertToBoolean(value) {
+        return JSON.parse(value.toLowerCase());
+    }
+
+    convertInteger(value) {
+        if (this.hasLeadingZero(value)) {
+            return String(value);
         }
-        return false;
+
+        const num = Number(value);
+        return Number.isSafeInteger(num) ? num : String(value);
+    }
+
+    convertFloat(value) {
+        const num = Number(value);
+        return Number.isFinite(num) ? num : String(value);
     }
 }