Added: Trim Characters Start

Author: Mqxx

src/format/trim_characters_start.test.ts

@@ -0,0 +1,77 @@
+import { assertEquals } from "https://deno.land/std@0.203.0/assert/assert_equals.ts";
+import trimCharactersStart from "./trim_characters_start.ts";
+
+Deno.test(
+    'Trim characters at the start of a string.',
+    async (test) => {
+        await test.step({
+            name: 'Empty input string, empty characters',
+            fn: () => {
+                assertEquals(
+                    trimCharactersStart('', ''),
+                    ''
+                )
+            }
+        })
+
+        await test.step({
+            name: 'Empty characters',
+            fn: () => {
+                assertEquals(
+                    trimCharactersStart('abc123', ''),
+                    'abc123'
+                )
+            }
+        })
+
+        await test.step({
+            name: 'Empty input string',
+            fn: () => {
+                assertEquals(
+                    trimCharactersStart('', 'abc'),
+                    ''
+                )
+            }
+        })
+
+        await test.step({
+            name: 'Fake Escaped characters in input string',
+            fn: () => {
+                assertEquals(
+                    trimCharactersStart('\aabc123\a', '\a'),
+                    'bc123\a'
+                )
+            }
+        })
+
+        await test.step({
+            name: 'Real Escaped characters in input string',
+            fn: () => {
+                assertEquals(
+                    trimCharactersStart('\ttabc123', '\t'),
+                    'tabc123'
+                )
+            }
+        })
+
+        await test.step({
+            name: 'Skip characters in input string',
+            fn: () => {
+                assertEquals(
+                    trimCharactersStart('abc123', '1'),
+                    'abc123'
+                )
+            }
+        })
+
+        await test.step({
+            name: 'Normal trim',
+            fn: () => {
+                assertEquals(
+                    trimCharactersStart('abc123', 'cab23'),
+                    '123'
+                )
+            }
+        })
+    }
+)

src/format/trim_characters_start.ts

@@ -0,0 +1,21 @@
+/**
+ * This function is similar to the standard `String.prototype.trimStart()` function. With this function, several
+ * characters can be specified as a string which are then trimmed at the start of the `inputString`.
+ * 
+ * @param inputString The input string to trim the start
+ * @param characters The characters to trim
+ * @returns The trimmed input string
+ */
+export default function trimCharactersStart(
+    inputString : string,
+    characters : string
+) : string {
+    const charactersSet = new Set(characters.split(''));
+    let startIndex = 0;
+
+    while (startIndex < inputString.length && charactersSet.has(inputString[startIndex])) {
+        startIndex++;
+    }
+
+    return inputString.substring(startIndex);
+}