feat: add uniqueArray helper function

2 files changed, 77 insertions, 0 deletions

diff --git a/lib/helpers.js b/lib/helpers.js
index 68e895e7..4ecdaab3 100644
--- a/lib/helpers.js
+++ b/lib/helpers.js
@@ -216,6 +216,35 @@ var Helpers = function (faker) {
   };
 
   /**
+   * takes an array of strings or function that returns a string
+   * and outputs a unique array of strings based on that source
+   * @example uniqueArray(faker.random.word, 50)
+   * @example uniqueArray(faker.definitions.name.first_name, 6)
+   * @example uniqueArray(["Hello", "World", "Goodbye"], 2)
+   * @method faker.helpers.uniqueArray
+   * @param {string[] | function => string} source
+   * @param {number} length
+   * @returns {string[]}
+  */
+  self.uniqueArray = function(source, length) {
+    if (Array.isArray(source)) {
+      const set = new Set(source);
+      const array = Array.from(set);
+      return faker.helpers.shuffle(array).splice(0, length);
+    }
+    const set = new Set();
+    try {
+      if (typeof source === "function") {
+        while (set.size < length) {
+          set.add(source());
+        }
+      }
+    } finally {
+      return Array.from(set);
+    }
+  };
+
+  /**
    * mustache
    *
    * @method faker.helpers.mustache
diff --git a/test/helpers.unit.js b/test/helpers.unit.js
index ec32dd02..c2f0adee 100644
--- a/test/helpers.unit.js
+++ b/test/helpers.unit.js
@@ -58,6 +58,54 @@ describe("helpers.js", function () {
     });
   });
 
+  describe("uniqueArray()", function () {
+    it("custom array returns unique array", function () {
+      var input = ["a", "a", "a", "a,", "a", "a", "a", "a", "b"];
+      var length = 2;
+      var unique = faker.helpers.uniqueArray(input, length);
+      assert.strictEqual(unique.length, length);
+      assert.strictEqual(new Set(unique).size, length);
+    });
+
+    it("definition array returns unique array", function () {
+      var length = faker.datatype.number({ min: 1, max: 6 });
+      var unique = faker.helpers.uniqueArray(faker.definitions.hacker.noun, length);
+      assert.strictEqual(unique.length, length);
+      assert.strictEqual(new Set(unique).size, length);
+    });
+
+    it("function returns unique array", function () {
+      var length = faker.datatype.number({ min: 1, max: 6 });
+      var unique = faker.helpers.uniqueArray(faker.lorem.word, length);
+      assert.strictEqual(unique.length, length);
+      assert.strictEqual(new Set(unique).size, length);
+    });
+
+    it("empty array returns empty array", function () {
+      var input = [];
+      var length = faker.datatype.number({ min: 1, max: 6 });
+      var unique = faker.helpers.uniqueArray(input, length);
+      assert.strictEqual(unique.length, input.length);
+      assert.strictEqual(new Set(unique).size, input.length);
+    });
+
+    it("length longer than source returns max length", function () {
+      var input = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j"];
+      var length = input.length + 1;
+      var unique = faker.helpers.uniqueArray(input, length);
+      assert.strictEqual(unique.length, input.length);
+      assert.strictEqual(new Set(unique).size, input.length);
+    });
+
+    it("works as expected when seeded", function () {
+      var input = ["a", "a", "a", "a", "a", "f", "g", "h", "i", "j"];
+      var length = 5;
+      faker.seed(100);
+      var unique = faker.helpers.uniqueArray(input, length);
+      assert.deepStrictEqual(unique, ["g", "a", "i", "f", "j"]);
+    });
+  });
+
   describe("slugify()", function () {
     it("removes unwanted characters from URI string", function () {
       assert.strictEqual(faker.helpers.slugify("Aiden.Harªann"), "Aiden.Harann");