simplify truncate code

benchmark/string/truncate.bench.ts

@@ -5,17 +5,17 @@ import { bench, describe } from "vitest";
 import { randomStringArray } from "../testData.js";
 
 describe("truncate", () => {
-    const stringArray = randomStringArray(200);
+    const stringArray = randomStringArray(500);
 
     bench("moderndash", () => {
         for (const str of stringArray) {
-            truncate(str);
+            truncate(str, { length: 8 });
         }
     });
 
     bench("lodash", () => {
         for (const str of stringArray) {
-            lodashVersion(str);
+            lodashVersion(str, { length: 8 });
         }
     });
 });

package/src/string/truncate.ts

@@ -1,61 +1,44 @@
-type Options = {
-    /**
-     * The maximum string length.
-     *
-     * Default: 30
-     */
-    length?: number;
-
-    /**
-     * The string to indicate text is omitted.
-     *
-     * Also named [ellipsis](https://developer.mozilla.org/en-US/docs/Web/CSS/text-overflow)
-     *
-     * Default: "...", you might want to use "…" (… U+02026) instead
-     */
-    omission?: string;
-
-    /**
-     * The separator pattern to truncate to.
-     *
-     * Default: none
-     */
-    separator?: string;
-};
-
 /**
  * Truncates a string if it's longer than the given maximum length.
- * The last characters of the truncated string are replaced with the omission
+ * The last characters of the truncated string are replaced with the ellipsis
  * string which defaults to "...".
  *
+ * @example
+ * truncate("Hello, world!", { length: 5 })
+ * // => "Hello..."
+ * 
+ * truncate("Hello, world!", { length: 5, ellipsis: " [...]" })
+ * // => "Hello [...]"
+ * 
+ * truncate("Hello, world!", { length: 5, separator: " " })
+ * // => "Hello, ..."
+ * 
  * @param str The string to truncate
  * @param options The options object
+ * @param options.length The maximum string length (default: 30)
+ * @param options.ellipsis The string to indicate text is omitted (default: "...")
+ * @param options.separator The separator pattern to truncate to (default: none)
  * @returns The truncated string
  */
-export function truncate(str: string, options?: Options) {
-    // https://stackoverflow.com/q/1199352
-    // https://github.com/Maggi64/moderndash/issues/155
-    // https://lodash.com/docs/4.17.15#truncate
 
-    const { length = 30, omission = "...", separator } = options ?? {};
+export function truncate(str: string, options?: { length?: number; ellipsis?: string; separator?: string }): string {
+    const { length = 30, ellipsis = "...", separator } = options ?? {};
+    if (str.length <= length) return str;
 
-    if (str.length <= length) {
-        return str;
-    }
+    const end = length - ellipsis.length;
+
+    if (end < 1) 
+        return ellipsis;
+
+    // Actually long enough to truncate the string
+    let truncated = str.slice(0, end);
 
-    let maxLength = length - omission.length;
-    if (maxLength < 0) {
-        maxLength = 0;
+    if (separator) {
+        const sepIndex = truncated.lastIndexOf(separator);
+        if (sepIndex > -1) {
+            truncated = truncated.slice(0, sepIndex);
+        }
     }
-    const subString = str.slice(
-        0,
-        // FYI .slice() is OK if maxLength > text.length
-        maxLength
-    );
 
-    return (
-        (separator
-            ? subString.slice(0, subString.lastIndexOf(separator))
-            : subString) + omission
-    );
+    return truncated + ellipsis;
 }

package/test/string/truncate.test.ts

@@ -19,13 +19,13 @@ it("should truncate string the given length", () => {
 });
 
 it("should support a `omission` option", () => {
-    expect(truncate(string, { omission: " [...]" })).toBe(
+    expect(truncate(string, { ellipsis: " [...]" })).toBe(
         "hi-diddly-ho there, neig [...]"
     );
 });
 
 it("should support empty `omission` option", () => {
-    expect(truncate(string, { omission: "" })).toBe(
+    expect(truncate(string, { ellipsis: "" })).toBe(
         "hi-diddly-ho there, neighborin"
     );
 });
@@ -41,9 +41,9 @@ it("should support a `separator` option", () => {
 });
 
 it("should treat negative `length` as `0`", () => {
-    [0, -2].forEach((length) => {
+    for (const length of [0, -2]) {
         expect(truncate(string, { length })).toBe("...");
-    });
+    }
 });
 
 it("should work as an iteratee for methods like `_.map`", () => {