Added Length operation

Added "Length" operation that returns the length of the input string. It can return in bytes, characters (i.e., Unicode), or JavaScript's UTF-16 units. (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/length)

src/core/config/Categories.json

@@ -225,6 +225,7 @@
             "Filter",
             "Head",
             "Tail",
+            "Length",
             "Count occurrences",
             "Expand alphabet range",
             "Drop bytes",

src/core/operations/Length.mjs

@@ -0,0 +1,61 @@
+/**
+ * @author David Byrne [davidribyrne@users.noreply.github.com]
+ * @copyright David Byrne 2020
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation.mjs";
+
+const BYTES = "Bytes";
+const CHARS = "Characters";
+const UTF = "UTF-16 units";
+
+/**
+ * Length operation
+ */
+class Length extends Operation {
+
+
+    /**
+     * Length constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Length";
+        this.module = "Default";
+        this.description = "Returns the input length.<br/><br/>" +
+                "<b>Bytes</b> - Number of bytes (Unicode characters may have up to 4 bytes)<br/>" +
+                "<b>Characters</b> - Number of Unicode characters<br/>" +
+                "<b>UTF-16 units</b> - See information URL for details ";
+        this.infoURL = "https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/length";
+        this.inputType = "string";
+        this.outputType = "number";
+        this.args = [
+            {
+                name: "First arg",
+                type: "option",
+                value: [BYTES, CHARS, UTF]
+            }
+        ];
+    }
+
+    /**
+     * @param {string} input
+     * @param {Object[]} args
+     * @returns {number}
+     */
+    run(input, args) {
+        switch (args[0]) {
+            case BYTES:
+                return new Blob([input]).size;
+            case CHARS:
+                return Array.from(input).length;
+            case UTF:
+                return input.length;
+        }
+    }
+
+}
+
+export default Length;