Adding Text.padStart function.

Author: iclanton

libraries/node-core-library/src/Text.ts

@@ -69,17 +69,43 @@ export class Text {
   }
 
   /**
-   * Append spaces to the end of a string to ensure the result has a minimum length.
+   * Append characters to the end of a string to ensure the result has a minimum length.
    * @remarks
    * If the string length already exceeds the minimum length, then the string is unchanged.
    * The string is not truncated.
    */
-  public static padEnd(s: string, minimumLength: number): string {
-    let result: string = s;
-    while (result.length < minimumLength) {
-      result += ' ';
+  public static padEnd(s: string, minimumLength: number, paddingCharacter: string = ' '): string {
+    if (paddingCharacter.length !== 1) {
+      throw new Error('The paddingCharacter parameter must be a single character.');
+    }
+
+    if (s.length < minimumLength) {
+      const paddingArray: string[] = new Array(minimumLength - s.length);
+      paddingArray.unshift(s);
+      return paddingArray.join(paddingCharacter);
+    } else {
+      return s;
+    }
+  }
+
+  /**
+   * Append characters to the start of a string to ensure the result has a minimum length.
+   * @remarks
+   * If the string length already exceeds the minimum length, then the string is unchanged.
+   * The string is not truncated.
+   */
+  public static padStart(s: string, minimumLength: number, paddingCharacter: string = ' '): string {
+    if (paddingCharacter.length !== 1) {
+      throw new Error('The paddingCharacter parameter must be a single character.');
+    }
+
+    if (s.length < minimumLength) {
+      const paddingArray: string[] = new Array(minimumLength - s.length);
+      paddingArray.push(s);
+      return paddingArray.join(paddingCharacter);
+    } else {
+      return s;
     }
-    return result;
   }
 
   /**

libraries/node-core-library/src/test/Text.test.ts

@@ -4,26 +4,73 @@
 import { Text } from '../Text';
 
 describe('Text', () => {
-  it('Text.padEnd()', () => {
-    expect(Text.padEnd('', 5)).toEqual(      '     ');
-    expect(Text.padEnd('123', 5)).toEqual(   '123  ');
-    expect(Text.padEnd('12345', 5)).toEqual( '12345');
-    expect(Text.padEnd('123456', 5)).toEqual('123456');
+  describe('padEnd', () => {
+    it('Throws an exception if the padding character isn\'t a single character', () => {
+      expect(() => Text.padEnd('123', 1, '')).toThrow();
+      expect(() => Text.padEnd('123', 1, '  ')).toThrow();
+    });
+
+    it('Doesn\'t change the string if it\'s already at or greater than the minimum length', () => {
+      expect(Text.padEnd('12345', 5)).toEqual( '12345');
+      expect(Text.padEnd('123456', 5)).toEqual('123456');
+      expect(Text.padEnd('12345', 5, '0')).toEqual( '12345');
+      expect(Text.padEnd('123456', 5, '0')).toEqual('123456');
+    });
+
+    it('Appends the default character (spaces) to the end of a string', () => {
+      expect(Text.padEnd('', 5)).toEqual(   '     ');
+      expect(Text.padEnd('123', 5)).toEqual('123  ');
+    });
+
+    it('Appends the characters to the end of a string', () => {
+      expect(Text.padEnd('', 5, '0')).toEqual(   '00000');
+      expect(Text.padEnd('123', 5, '0')).toEqual('12300');
+    });
+  });
+
+  describe('padStart', () => {
+    it('Throws an exception if the padding character isn\'t a single character', () => {
+      expect(() => Text.padStart('123', 1, '')).toThrow();
+      expect(() => Text.padStart('123', 1, '  ')).toThrow();
+    });
+
+    it('Doesn\'t change the string if it\'s already at or greater than the minimum length', () => {
+      expect(Text.padStart('12345', 5)).toEqual( '12345');
+      expect(Text.padStart('123456', 5)).toEqual('123456');
+      expect(Text.padStart('12345', 5, '0')).toEqual( '12345');
+      expect(Text.padStart('123456', 5, '0')).toEqual('123456');
+    });
+
+    it('Appends the default character (spaces) to the end of a string', () => {
+      expect(Text.padStart('', 5)).toEqual(   '     ');
+      expect(Text.padStart('123', 5)).toEqual('  123');
+    });
+
+    it('Appends the characters to the end of a string', () => {
+      expect(Text.padStart('', 5, '0')).toEqual(   '00000');
+      expect(Text.padStart('123', 5, '0')).toEqual('00123');
+    });
   });
-  it('Text.truncateWithEllipsis()', () => {
-    expect(() => {
-      Text.truncateWithEllipsis('123', -1);
-    }).toThrow();
-    expect(Text.truncateWithEllipsis('123', 0)).toEqual(   '');
-
-    expect(Text.truncateWithEllipsis('', 2)).toEqual(      '');
-    expect(Text.truncateWithEllipsis('1', 2)).toEqual(     '1');
-    expect(Text.truncateWithEllipsis('12', 2)).toEqual(    '12');
-    expect(Text.truncateWithEllipsis('123', 2)).toEqual(   '12');
-
-    expect(Text.truncateWithEllipsis('123', 5)).toEqual(   '123');
-    expect(Text.truncateWithEllipsis('1234', 5)).toEqual(  '1234');
-    expect(Text.truncateWithEllipsis('12345', 5)).toEqual( '12345');
-    expect(Text.truncateWithEllipsis('123456', 5)).toEqual('12...');
+
+  describe('truncateWithEllipsis', () => {
+    it('Throws an exception if the maximum length is less than zero', () => {
+      expect(() => Text.truncateWithEllipsis('123', -1)).toThrow();
+    });
+
+    it('Doesn\'t change the string if it\'s already shorter than the maximum length', () => {
+      expect(Text.truncateWithEllipsis('', 2)).toEqual(      '');
+      expect(Text.truncateWithEllipsis('1', 2)).toEqual(     '1');
+      expect(Text.truncateWithEllipsis('12', 2)).toEqual(    '12');
+
+      expect(Text.truncateWithEllipsis('123', 5)).toEqual(   '123');
+      expect(Text.truncateWithEllipsis('1234', 5)).toEqual(  '1234');
+    });
+
+    it('Truncates strings', () => {
+      expect(Text.truncateWithEllipsis('123', 0)).toEqual(   '');
+      expect(Text.truncateWithEllipsis('123', 2)).toEqual(   '12');
+      expect(Text.truncateWithEllipsis('12345', 5)).toEqual( '12345');
+      expect(Text.truncateWithEllipsis('123456', 5)).toEqual('12...');
+    });
   });
 });