jsgen: implement array map and filter

vlib/v/gen/js/js.v

@@ -1122,9 +1122,41 @@ fn (mut g JsGen) gen_call_expr(it ast.CallExpr) {
 		name = g.js_name(it.name)
 	}
 	g.expr(it.left)
-	if it.is_method {
-		// example: foo.bar.baz()
+	if it.is_method { // foo.bar.baz()
+		sym := g.table.get_type_symbol(it.receiver_type)
 		g.write('.')
+
+		if sym.kind == .array && it.name in ['map', 'filter'] {
+			// Prevent 'it' from getting shadowed inside the match
+			node := it
+			g.write(it.name)
+			g.write('(')
+			match node.args[0].expr {
+				ast.AnonFn {
+					g.gen_fn_decl(it.decl)
+						g.write(')')
+						return
+					}
+				ast.Ident {
+					if it.kind == .function {
+						g.write(g.js_name(it.name))
+						g.write(')')
+						return
+					} else if it.kind == .variable {
+						v_sym := g.table.get_type_symbol(it.var_info().typ)
+						if v_sym.kind == .function {
+							g.write(g.js_name(it.name))
+							g.write(')')
+							return
+						}
+					}
+				} else {}
+			}
+			g.write('it => ')
+			g.expr(node.args[0].expr)
+			g.write(')')
+			return
+		}
 	} else {
 		if name in builtin_globals {
 			g.write('builtin.')

vlib/v/gen/js/tests/array.js

@@ -1,5 +1,5 @@
-// V_COMMIT_HASH 808975f
-// V_CURRENT_COMMIT_HASH 564545d
+// V_COMMIT_HASH 8a24d7d
+// V_CURRENT_COMMIT_HASH 6f886dc
 // Generated by the V compiler
 
 "use strict";
@@ -33,6 +33,24 @@ const builtin = (function () {
 
 /** @namespace main */
 const main = (function () {
+	/**
+	 * @function
+	 * @param {string} s
+	 * @returns {string}
+	*/
+	function map_cb(s) {
+		return `CB: ${s}`;
+	}
+	
+	/**
+	 * @function
+	 * @param {number} n
+	 * @returns {boolean}
+	*/
+	function filter_cb(n) {
+		return n < 4;
+	}
+	
 	/**
 	 * @function
 	 * @param {...number} args
@@ -79,7 +97,7 @@ const main = (function () {
 		builtin.print("Back\t=> ");
 		builtin.println(slice4);
 		/** @type {number} */
-		const idx2 = "😀".charCodeAt(0);
+		const idx2 = slice4.charCodeAt(0);
 		builtin.print("66\t=> ");
 		builtin.println(idx2);
 		/** @type {Map<string, string>} */
@@ -113,6 +131,40 @@ const main = (function () {
 			builtin.println(v);
 		}
 		
+		/** @type {string[]} */
+		const a = arr1.map(it => `VAL: ${it}`);
+		/** @type {string[]} */
+		const b = arr1.map(map_cb);
+		/** @type {string[]} */
+		const c = arr1.map(it => map_cb(it));
+		/** @type {string[]} */
+		const d = arr1.map(function (a) {
+			const _tmp3 = a;
+			return `ANON: ${a}`;
+		});
+		/** @type {number[]} */
+		const e = arr1.map(it => 456);
+		builtin.println(a);
+		builtin.println(b);
+		builtin.println(c);
+		builtin.println(d);
+		builtin.println(e);
+		builtin.println("\n\n");
+		/** @type {number[]} */
+		const aa = arr2.filter(it => it < 4);
+		/** @type {number[]} */
+		const bb = arr2.filter(filter_cb);
+		/** @type {number[]} */
+		const cc = arr2.filter(it => filter_cb(it));
+		/** @type {number[]} */
+		const dd = arr2.filter(function (a) {
+			const _tmp4 = a;
+			return a < 4;
+		});
+		builtin.println(aa);
+		builtin.println(bb);
+		builtin.println(cc);
+		builtin.println(dd);
 	})();
 
 	/* module exports */

vlib/v/gen/js/tests/array.v

@@ -1,3 +1,6 @@
+fn map_cb(s string) string { return 'CB: $s' }
+fn filter_cb(n int) bool { return n < 4 }
+
 fn variadic(args ...int) {
 	println(args)
 	println(args[0])
@@ -70,3 +73,33 @@ println('0 to 8\t=>')
 for i, _ in arr2 { println(i) }
 println('\n\n4 to 5\t=> ')
 for _, v in slice3 { println(v) }
+
+println('\n\n')
+
+// map
+a := arr1.map('VAL: $it')
+b := arr1.map(map_cb)
+c := arr1.map(map_cb(it))
+d := arr1.map(fn(a string) string { return 'ANON: $a' })
+// I don't know when this would ever be used,
+// but it's what the C backend does ¯\_(ツ)_/¯
+e := arr1.map(456)
+
+println(a)
+println(b)
+println(c)
+println(d)
+println(e)
+
+println('\n\n')
+
+// filter
+aa := arr2.filter(it < 4)
+bb := arr2.filter(filter_cb)
+cc := arr2.filter(filter_cb(it))
+dd := arr2.filter(fn(a int) bool { return a < 4 })
+
+println(aa)
+println(bb)
+println(cc)
+println(dd)