Add new string operators: length, join, split, concat etc.

core/modules/filters/strings.js

@@ -0,0 +1,70 @@
+/*\
+title: $:/core/modules/filters/strings.js
+type: application/javascript
+module-type: filteroperator
+
+Filter operators for strings. Unary/binary operators work on each item in turn, and return a new item list.
+
+Sum/product/maxall/minall operate on the entire list, returning a single item.
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+exports.length = makeStringBinaryOperator(
+	function(a) {return [("" + a).length];}
+);
+
+exports.uppercase = makeStringBinaryOperator(
+	function(a) {return [("" + a).toUpperCase()];}
+);
+
+exports.lowercase = makeStringBinaryOperator(
+	function(a) {return [("" + a).toLowerCase()];}
+);
+
+exports.trim = makeStringBinaryOperator(
+	function(a) {return [$tw.utils.trim(a)];}
+);
+
+exports.concat = makeStringBinaryOperator(
+	function(a,b) {return ["" + a + b];}
+);
+
+exports.split = makeStringBinaryOperator(
+	function(a,b) {return [("" + a).split(b)];}
+);
+
+exports.join = makeStringArrayOperator(
+	function(accumulator,value,operand) {
+		return "" + (accumulator ? accumulator + (operand || "") + value : value);
+	}
+);
+
+function makeStringBinaryOperator(fnCalc) {
+	return function(source,operator,options) {
+		var result = [];
+		source(function(tiddler,title) {
+			Array.prototype.push.apply(result,fnCalc(title,operator.operand || ""));
+		});
+		return result;
+	};
+}
+
+function makeStringArrayOperator(fnCalc,initialValue) {
+	initialValue = initialValue || "";
+	return function(source,operator,options) {
+		var result = [];
+		source(function(tiddler,title) {
+			result.push(title);
+		});
+		return [result.reduce(function(accumulator,currentValue) {
+			return fnCalc(accumulator,currentValue,operator.operand || "");
+		},initialValue)];
+	};
+}
+
+})();

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

@@ -361,7 +361,17 @@ describe("Filter tests", function() {
 		expect(wiki.filterTiddlers("[list[TiddlerSeventh]before[MissingTiddler]]").join(",")).toBe("a fourth tiddler");
 	});
 
-	it("should handle the math operators", function() {
+	it("should handle the string operators", function() {
+		expect(wiki.filterTiddlers("John Paul George Ringo +[length[]]").join(",")).toBe("4,4,6,5");
+		expect(wiki.filterTiddlers("John Paul George Ringo +[uppercase[]]").join(",")).toBe("JOHN,PAUL,GEORGE,RINGO");
+		expect(wiki.filterTiddlers("John Paul George Ringo +[lowercase[]]").join(",")).toBe("john,paul,george,ringo");
+		expect(wiki.filterTiddlers("John Paul George Ringo +[concat[y]]").join(",")).toBe("Johny,Pauly,Georgey,Ringoy");
+		expect(wiki.filterTiddlers("John Paul George Ringo +[split[]]").join(",")).toBe("J,o,h,n,P,a,u,l,G,e,o,r,g,e,R,i,n,g,o");
+		expect(wiki.filterTiddlers("John Paul George Ringo +[join[ ]split[e]join[ee]split[ ]]").join(",")).toBe("John,Paul,G,org,,Ringo");
+		expect(wiki.filterTiddlers("[[ John ]] [[Paul ]] [[ George]] Ringo +[trim[]join[-]]").join(",")).toBe("John-Paul-George-Ringo");
+	});
+
+	it("should handle the mathematics operators", function() {
 		expect(wiki.filterTiddlers("[[2]add[2]]").join(",")).toBe("4");
 		expect(wiki.filterTiddlers("[[4]subtract[2]]").join(",")).toBe("2");
 		expect(wiki.filterTiddlers("[[24]divide[8]]").join(",")).toBe("3");