Update and rename randomString.md to randomAlphaNumeric.md

snippets/randomAlphaNumeric.md

@@ -0,0 +1,27 @@
+---
+title: randomAlphaNumeric
+tags: string,random,advanced
+---
+
+Returns a random string with the specified length.
+
+- Use `Array.from()` to create a new array with the specified `length`.
+- Use `Math.random()` generate a random floating-point number, `Number.prototype.toString(36)` to convert it to an alphanumeric string.
+- Use `String.prototype.slice(2)` to remove the integral part and decimal point from each generated number.
+- Use `Array.prototype.some()` to repeat this process as many times as required, up to `length`, as it produces a variable-length string each time.
+- Finally, use `String.prototype.slice()` to trim down the generated string if it's longer than the given `length`.
+
+```js
+const randomAlphaNumeric = length => {
+  let s = '';
+  Array.from({ length }).some(() => {
+    s += Math.random().toString(36).slice(2);
+    return s.length >= length;
+  });
+  return s.slice(0, length);
+};
+```
+
+```js
+randomAlphaNumeric(5); // '0afad'
+```