feat(text/unstable): add strip function (denoland#6265)

text/deno.json

@@ -7,6 +7,7 @@
     "./compare-similarity": "./compare_similarity.ts",
     "./levenshtein-distance": "./levenshtein_distance.ts",
     "./unstable-slugify": "./unstable_slugify.ts",
+    "./unstable-strip": "./unstable_strip.ts",
     "./to-camel-case": "./to_camel_case.ts",
     "./unstable-to-constant-case": "./unstable_to_constant_case.ts",
     "./to-kebab-case": "./to_kebab_case.ts",

text/unstable_strip.ts

@@ -0,0 +1,102 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+import { escape } from "@std/regexp";
+
+export type StripOptions = {
+  /**
+   * If `true`, all occurrences will be stripped from the start of the string.
+   * If a number, the specified number of occurrences will be stripped from the start.
+   *
+   * @default {true} // if `end` option is omitted
+   * @default {false} // if `end` option is specified
+   */
+  start?: boolean | number;
+  /**
+   * If `true`, all occurrences will be stripped from the end of the string.
+   * If a number, the specified number of occurrences will be stripped from the end.
+   *
+   * @default {true} // if `start` option is omitted
+   * @default {false} // if `start` option is specified
+   */
+  end?: boolean | number;
+};
+
+/**
+ * Strips the specified pattern from the start and/or end of the string.
+ *
+ * @param str The string to strip from.
+ * @param pattern The pattern to strip from the string.
+ * @param options An object containing options for the strip operation.
+ *
+ * @example Strip both start and end
+ * ```ts
+ * import { strip } from "@std/text/unstable-strip";
+ * import { assertEquals } from "@std/assert";
+ * assertEquals(strip("---x---", "-"), "x");
+ * ```
+ *
+ * @example Strip start only
+ * ```ts
+ * import { strip } from "@std/text/unstable-strip";
+ * import { assertEquals } from "@std/assert";
+ * assertEquals(strip("---x---", "-", { start: true }), "x---");
+ * ```
+ *
+ * @example Strip end only
+ * ```ts
+ * import { strip } from "@std/text/unstable-strip";
+ * import { assertEquals } from "@std/assert";
+ * assertEquals(strip("---x---", "-", { end: true }), "---x");
+ * ```
+ *
+ * @example Strip a given number of occurrences
+ * ```ts
+ * import { strip } from "@std/text/unstable-strip";
+ * import { assertEquals } from "@std/assert";
+ * assertEquals(strip("---x---", "-", { start: 2, end: 1 }), "-x--");
+ * ```
+ *
+ * @example Strip using a regexp
+ * ```ts
+ * import { strip } from "@std/text/unstable-strip";
+ * import { assertEquals } from "@std/assert";
+ * assertEquals(strip("-_-x-_-", /[-_]/), "x");
+ * ```
+ */
+export function strip(
+  str: string,
+  pattern: string | RegExp,
+  options?: StripOptions,
+): string {
+  const source = typeof pattern === "string" ? escape(pattern) : pattern.source;
+  const flags = typeof pattern === "string" ? "" : getFlags(pattern);
+
+  const start = options?.start ?? (options?.end == null ? true : false);
+  const end = options?.end ?? (options?.start == null ? true : false);
+
+  let prev = str;
+
+  for (
+    const [option, regex] of [
+      [start, new RegExp(`^${source}`, flags)],
+      [end, new RegExp(`${source}$`, flags)],
+    ] as const
+  ) {
+    const count = typeof option === "number" ? option : option ? Infinity : 0;
+
+    for (let i = 0; i < count; ++i) {
+      str = str.replace(regex, "");
+      if (str === prev) break;
+      prev = str;
+    }
+  }
+
+  return str;
+}
+
+function getFlags(re: RegExp): string {
+  const flags = new Set(re.flags);
+  flags.delete("g");
+  flags.delete("y");
+
+  return [...flags.keys()].join("");
+}

text/unstable_strip_test.ts

@@ -0,0 +1,31 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+import { assertEquals } from "@std/assert";
+import { strip } from "./unstable_strip.ts";
+
+Deno.test("strip()", async (t) => {
+  await t.step("strips single-char prefixes/suffixes", () => {
+    assertEquals(strip("..x.x..", "."), "x.x");
+
+    assertEquals(strip("..x.x..", ".", { start: true }), "x.x..");
+    assertEquals(strip("..x.x..", ".", { end: true }), "..x.x");
+
+    assertEquals(strip("..x.x..", ".", { end: 0 }), "..x.x..");
+    assertEquals(strip("..x.x..", ".", { end: 1 }), "..x.x.");
+    assertEquals(strip("..x.x..", ".", { end: 2 }), "..x.x");
+    assertEquals(strip("..x.x..", ".", { end: 3 }), "..x.x");
+
+    assertEquals(strip("..x.x..", ".", { start: 0 }), "..x.x..");
+    assertEquals(strip("..x.x..", ".", { start: 1 }), ".x.x..");
+    assertEquals(strip("..x.x..", ".", { start: 2 }), "x.x..");
+    assertEquals(strip("..x.x..", ".", { start: 3 }), "x.x..");
+  });
+
+  await t.step("strips mult-char prefixes/suffixes", () => {
+    assertEquals(strip("._.._._.x.x._._.._.", "._."), "_.x.x._");
+  });
+
+  await t.step("strips prefixes/suffixes by regex pattern", () => {
+    assertEquals(strip("!@#$%x.x!@#$%", /./), "");
+    assertEquals(strip("!@#$%x.x!@#$%", /[^\p{L}\p{M}\p{N}]+/u), "x.x");
+  });
+});