TypeScriptToLua · Perryvw · Dec 11, 2019 · Dec 8, 2019 · Dec 8, 2019 · Dec 9, 2019
diff --git a/src/LuaLib.ts b/src/LuaLib.ts
@@ -61,6 +61,9 @@ export enum LuaLibFeature {
     StringReplace = "StringReplace",
     StringSplit = "StringSplit",
     StringStartsWith = "StringStartsWith",
+    StringTrim = "StringTrim",
+    StringTrimEnd = "StringTrimEnd",
+    StringTrimStart = "StringTrimStart",
     Symbol = "Symbol",
     SymbolRegistry = "SymbolRegistry",
     TypeOf = "TypeOf",

diff --git a/src/lualib/StringTrim.ts b/src/lualib/StringTrim.ts
@@ -0,0 +1,5 @@
+function __TS__StringTrim(this: string): string {
+    // http://lua-users.org/wiki/StringTrim
+    const [result] = string.gsub(this, "^[%s\xA0\uFEFF]*(.-)[%s\xA0\uFEFF]*$", "%1");
+    return result;
+}
diff --git a/src/lualib/StringTrimEnd.ts b/src/lualib/StringTrimEnd.ts
@@ -0,0 +1,5 @@
+function __TS__StringTrimEnd(this: string): string {
+    // http://lua-users.org/wiki/StringTrim
+    const [result] = string.gsub(this, "[%s\xA0\uFEFF]*$", "");
+    return result;
+}
diff --git a/src/lualib/StringTrimStart.ts b/src/lualib/StringTrimStart.ts
@@ -0,0 +1,5 @@
+function __TS__StringTrimStart(this: string): string {
+    // http://lua-users.org/wiki/StringTrim
+    const [result] = string.gsub(this, "^[%s\xA0\uFEFF]*", "");
+    return result;
+}
diff --git a/src/transformation/builtins/string.ts b/src/transformation/builtins/string.ts
@@ -94,6 +94,14 @@ export function transformStringPrototypeCall(
             return createStringCall("lower", node, caller);
         case "toUpperCase":
             return createStringCall("upper", node, caller);
+        case "trim":
+            return transformLuaLibFunction(context, LuaLibFeature.StringTrim, node, caller);
+        case "trimEnd":
+        case "trimRight":
+            return transformLuaLibFunction(context, LuaLibFeature.StringTrimEnd, node, caller);
+        case "trimStart":
+        case "trimLeft":
+            return transformLuaLibFunction(context, LuaLibFeature.StringTrimStart, node, caller);
         case "split":
             return transformLuaLibFunction(context, LuaLibFeature.StringSplit, node, caller, ...params);
         case "charAt":

diff --git a/test/unit/builtins/string.spec.ts b/test/unit/builtins/string.spec.ts
@@ -265,3 +265,25 @@ test.each([
         `;
     expect(util.transpileAndExecute(code)).toBe(6);
 });
+
+const trimTestCases = [
+    "",
+    " ",
+    "\t",
+    "\t \t",
+    " foo ",
+    "\tfoo\t",
+    "\ffoo\f",
+    "\vfoo\v",
+    "\uFEFFFoo\uFEFF",
+    "\xA0Foo\xA0",
+    " \t foo \t ",
+    " foo    bar ",
+    "\r\nfoo\n\r\n",
+    "\r\nfoo\nbar\n\r\n",
+];
+describe.each(["trim", "trimEnd", "trimRight", "trimStart", "trimLeft"])("string.%s", trim => {
+    test.each(trimTestCases)("matches JS result (%p)", testString => {
+        util.testExpression`${util.formatCode(testString)}.${trim}()`.expectToMatchJsResult();
+    });
+});