Merge pull request #322 from ckeditor/i/6188

Other: The `uid()` helper should be a lot faster. Closes ckeditor/ckeditor5#6188.

src/uid.js

@@ -7,18 +7,53 @@
  * @module utils/uid
  */
 
+// A hash table of hex numbers to avoid using toString() in uid() which is costly.
+// [ '00', '01', '02', ..., 'fe', 'ff' ]
+const HEX_NUMBERS = new Array( 256 ).fill()
+	.map( ( val, index ) => ( '0' + ( index ).toString( 16 ) ).slice( -2 ) );
+
 /**
- * Returns a unique id. This id consist of an 'e' character and a randomly generated string of 32 aphanumeric characters.
- * Each character in uid string represents a hexadecimal digit (base 16).
+ * Returns a unique id. The id starts with an "e" character and a randomly generated string of
+ * 32 alphanumeric characters.
+ *
+ * **Note**: The characters the unique id is built from correspond to the hex number notation
+ * (from "0" to "9", from "a" to "f"). In other words, each id corresponds to an "e" followed
+ * by 16 8-bit numbers next to each other.
  *
- * @returns {String} A hexadecimal number representing the id.
+ * @returns {String} An unique id string.
  */
 export default function uid() {
-	let uuid = 'e'; // Make sure that id does not start with number.
-
-	for ( let i = 0; i < 8; i++ ) {
-		uuid += Math.floor( ( 1 + Math.random() ) * 0x10000 ).toString( 16 ).substring( 1 );
-	}
+	// Let's create some positive random 32bit integers first.
+	//
+	// 1. Math.random() is a float between 0 and 1.
+	// 2. 0x100000000 is 2^32 = 4294967296.
+	// 3. >>> 0 enforces integer (in JS all numbers are floating point).
+	//
+	// For instance:
+	//		Math.random() * 0x100000000 = 3366450031.853859
+	// but
+	//		Math.random() * 0x100000000 >>> 0 = 3366450031.
+	const r1 = Math.random() * 0x100000000 >>> 0;
+	const r2 = Math.random() * 0x100000000 >>> 0;
+	const r3 = Math.random() * 0x100000000 >>> 0;
+	const r4 = Math.random() * 0x100000000 >>> 0;
 
-	return uuid;
+	// Make sure that id does not start with number.
+	return 'e' +
+		HEX_NUMBERS[ r1 >> 0 & 0xFF ] +
+		HEX_NUMBERS[ r1 >> 8 & 0xFF ] +
+		HEX_NUMBERS[ r1 >> 16 & 0xFF ] +
+		HEX_NUMBERS[ r1 >> 24 & 0xFF ] +
+		HEX_NUMBERS[ r2 >> 0 & 0xFF ] +
+		HEX_NUMBERS[ r2 >> 8 & 0xFF ] +
+		HEX_NUMBERS[ r2 >> 16 & 0xFF ] +
+		HEX_NUMBERS[ r2 >> 24 & 0xFF ] +
+		HEX_NUMBERS[ r3 >> 0 & 0xFF ] +
+		HEX_NUMBERS[ r3 >> 8 & 0xFF ] +
+		HEX_NUMBERS[ r3 >> 16 & 0xFF ] +
+		HEX_NUMBERS[ r3 >> 24 & 0xFF ] +
+		HEX_NUMBERS[ r4 >> 0 & 0xFF ] +
+		HEX_NUMBERS[ r4 >> 8 & 0xFF ] +
+		HEX_NUMBERS[ r4 >> 16 & 0xFF ] +
+		HEX_NUMBERS[ r4 >> 24 & 0xFF ];
 }