feat(chunk20): bchjs.Util.chunk20() - chunk array into 20-element arrays

src/util.js

@@ -97,6 +97,59 @@ class Util {
     return tempNum
   }
 
+  /**
+   * @api util.chunk20() chunk20()
+   * @apiName chunk20
+   * @apiGroup Util
+   * @apiDescription chunk up an array into multiple arrays of 20 elements each.
+   * Input: arrayToSlice - a one-dimensional array of elements.
+   * Returns a two-dimensional array. An array of 20-element arrays.
+   *
+   * @apiExample Example usage:
+   * (async () => {
+   *   try {
+   *      const bigArray = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26]
+   *
+   *      const chunked = bchjs.Util.chunk20(bigArray)
+   *      console.log(chunked)
+   *   } catch(error) {
+   *      console.error(error)
+   *   }
+   * })()
+   *
+   * // returns
+   *  [
+   *    [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19],
+   *    [20,21,22,23,24,25,26]
+   *  ]
+   */
+  // chunk20 - chunk up an array into multiple arrays of 20 elements each.
+  // Input: arrayToSlice - a one-dimensional array of elements.
+  // Returns a two-dimensional array. An array of 20-element arrays.
+  chunk20 (arrayToSlice) {
+    try {
+      // Validate inputs
+      if (!Array.isArray(arrayToSlice)) {
+        throw new Error('input must be an array')
+      }
+
+      let offset = 0
+      const result = []
+
+      // Loop over the array and slice off chunks of 20 elements.
+      while (offset < arrayToSlice.length) {
+        const chunk = arrayToSlice.slice(offset, offset + 20)
+        result.push(chunk)
+        offset = offset + 20
+      }
+
+      return result
+    } catch (err) {
+      console.error('Error in chunk20()')
+      throw err
+    }
+  }
+
   /**
    * @api util.validateAddress() validateAddress()
    * @apiName Validate Address.

test/unit/util.js

@@ -99,4 +99,77 @@ describe('#Util', () => {
       assert2.equal(result, 1.2)
     })
   })
+
+  describe('#chunk20', () => {
+    const thirtyFiveElements = [
+      0,
+      1,
+      2,
+      3,
+      4,
+      5,
+      6,
+      7,
+      8,
+      9,
+      10,
+      11,
+      12,
+      13,
+      14,
+      15,
+      16,
+      17,
+      18,
+      19,
+      20,
+      21,
+      22,
+      23,
+      24,
+      25,
+      26,
+      27,
+      28,
+      29,
+      30,
+      31,
+      32,
+      33,
+      34
+    ]
+
+    it('should split 35 elements into 2 arrays', () => {
+      const result = bchjs.Util.chunk20(thirtyFiveElements)
+      // console.log(`result: ${JSON.stringify(result, null, 2)}`)
+
+      assert2.isArray(result)
+      assert2.isArray(result[0])
+      assert2.equal(result.length, 2)
+      assert2.equal(result[0].length, 20)
+    })
+
+    it('should return accurately with an array of less than 20 elements', () => {
+      const elems = [0, 1, 2, 3, 4, 5]
+
+      const result = bchjs.Util.chunk20(elems)
+      // console.log(`result: ${JSON.stringify(result, null, 2)}`)
+
+      assert2.isArray(result)
+      assert2.isArray(result[0])
+      assert2.equal(result.length, 1)
+      assert2.equal(result[0].length, 6)
+    })
+
+    it('should throw an error for non-array input', () => {
+      try {
+        bchjs.Util.chunk20('string')
+
+        assert2.equal(true, false, 'Unexpected result')
+      } catch (err) {
+        // console.log(err)
+        assert2.include(err.message, 'input must be an array')
+      }
+    })
+  })
 })