Add charcode operator to make it easier to generate strings containing control characters

Avoids some confusing hacks. @saqimtiaz I'm guessing you might have already done something like this?

core/modules/filters/strings.js

@@ -172,4 +172,14 @@ exports.pad = function(source,operator,options) {
 	return results;
 }
 
+exports.charcode = function(source,operator,options) {
+	var chars = [];
+	$tw.utils.each(operator.operands,function(operand) {
+		if(operand !== "") {
+			chars.push(String.fromCharCode($tw.utils.parseInt(operand)));
+		}
+	});
+	return [chars.join("")];
+};
+
 })();

editions/test/tiddlers/tests/test-filters.js

@@ -819,6 +819,12 @@ function runTests(wiki) {
 	expect(wiki.filterTiddlers("[deserializers[]]").join(",")).toBe("application/javascript,application/json,application/x-tiddler,application/x-tiddler-html-div,application/x-tiddlers,text/css,text/html,text/plain");
 	});
 	
+	it("should handle the charcode operator", function() {
+		expect(wiki.filterTiddlers("[charcode[9]]").join(" ")).toBe(String.fromCharCode(9));
+		expect(wiki.filterTiddlers("[charcode[9],[10]]").join(" ")).toBe(String.fromCharCode(9) + String.fromCharCode(10));
+		expect(wiki.filterTiddlers("[charcode[]]").join(" ")).toBe("");
+	});
+
 }
 
 });

editions/tw5.com/tiddlers/filters/charcode.tid

@@ -0,0 +1,17 @@
+caption: charcode
+created: 20210622214425635
+modified: 20210622214425635
+op-input: ignored
+op-output: a string formed from concatenating the characters specified by the numeric codes given in the operand(s)
+op-parameter: numeric character code
+op-parameter-name: C
+op-purpose: generates string characters from their numeric character codes
+tags: [[Filter Operators]]
+title: charcode Operator
+type: text/vnd.tiddlywiki
+
+<<.from-version "5.1.24">>
+
+This operator returns a string formed from concatenating the characters specified by the numeric codes given in one or more operands. It is useful for generating special characters such as tab (`charcode[9]`) or new line (`charcode[13],[10]`).
+
+<<.operator-examples "charcode">>

editions/tw5.com/tiddlers/filters/examples/charcode.tid

@@ -0,0 +1,7 @@
+created: 20210622214849214
+modified: 20210622214849214
+tags: [[charcode Operator]] [[Operator Examples]]
+title: charcode Operator (Examples)
+type: text/vnd.tiddlywiki
+
+<<.operator-example 1 "[charcode[65]match[A]]">>