Added regex_count function

Author: jasny

README.md

@@ -412,6 +412,21 @@ regex_replace('/world/', 'universe', 'hello world')
 // "hello universe"
 ```
 
+### `regex_count`
+**Syntax**:
+```jmespath
+regex_count(regex, string)
+```
+
+**Description**:
+Counts the number of matches of a regular expression in a string.
+
+**Example**:
+```jmespath
+regex_count('/\\w+/g', 'hello world')
+// 2
+```
+
 ## More Resources
 
 The example above only shows a small amount of what

src/Runtime.ts

@@ -710,6 +710,10 @@ export class Runtime {
     return val.replace(this.parseRegexString(regexp), repl);
   };
 
+  private functionRegexCount: RuntimeFunction<[string, string], number> = ([regexp, val]) => {
+    return Array.from(val.matchAll(this.parseRegexString(regexp))).length;
+  };
+
   private functionTable: FunctionTable = {
     abs: {
       _func: this.functionAbs,
@@ -1272,5 +1276,16 @@ export class Runtime {
         },
       ],
     },
+    regex_count: {
+      _func: this.functionRegexCount,
+      _signature: [
+        {
+          types: [InputArgument.TYPE_STRING],
+        },
+        {
+          types: [InputArgument.TYPE_STRING],
+        },
+      ],
+    },
   };
 }

test/jmespath-functions.spec.ts

@@ -210,6 +210,10 @@ describe('Added functions', () => {
     expect(search('hello world', "regex_replace('/w\\w+d/', 'planet', @)")).toEqual('hello planet');
     expect(search('hello world', "regex_replace('/[aeoiu]/g', '*', @)")).toEqual('h*ll* w*rld');
   });
+
+  it('regex_count', () => {
+    expect(search('hello world', "regex_count('/\\w+/g', @)")).toEqual(2);
+  });
 });
 
 describe('custom functions', () => {