feat: add optional chaining support (?.)

Standard syntax: obj.val?.prop obj.val?.[expr] obj.arr?.[index] obj.func?.(args)
EricSmekens · Sep 26, 2021 · 56d1e3d · 56d1e3d
1 parent 01b9efb
commit 56d1e3d
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Showing 2 changed files with 33 additions and 11 deletions.
diff --git a/src/jsep.js b/src/jsep.js
@@ -558,19 +558,20 @@ export class Jsep {
 		this.gobbleSpaces();
 
 		let ch = this.code;
-		while (ch === Jsep.PERIOD_CODE || ch === Jsep.OBRACK_CODE || ch === Jsep.OPAREN_CODE) {
-			this.index++;
-
-			if (ch === Jsep.PERIOD_CODE) {
+		while (ch === Jsep.PERIOD_CODE || ch === Jsep.OBRACK_CODE || ch === Jsep.OPAREN_CODE || ch === Jsep.QUMARK_CODE) {
+			let optional;
+			if (ch === Jsep.QUMARK_CODE) {
+				if (this.expr.charCodeAt(this.index + 1) !== Jsep.PERIOD_CODE) {
+					break;
+				}
+				optional = true;
+				this.index += 2;
 				this.gobbleSpaces();
-				node = {
-					type: Jsep.MEMBER_EXP,
-					computed: false,
-					object: node,
-					property: this.gobbleIdentifier(),
-				};
+				ch = this.code;
 			}
-			else if (ch === Jsep.OBRACK_CODE) {
+			this.index++;
+
+			if (ch === Jsep.OBRACK_CODE) {
 				node = {
 					type: Jsep.MEMBER_EXP,
 					computed: true,
@@ -592,6 +593,23 @@ export class Jsep {
 					callee: node
 				};
 			}
+			else if (ch === Jsep.PERIOD_CODE || optional) {
+				if (optional) {
+					this.index--;
+				}
+				this.gobbleSpaces();
+				node = {
+					type: Jsep.MEMBER_EXP,
+					computed: false,
+					object: node,
+					property: this.gobbleIdentifier(),
+				};
+			}
+
+			if (optional) {
+				node.optional = true;
+			} // else leave undefined for compatibility with esprima
+
 			this.gobbleSpaces();
 			ch = this.code;
 		}

diff --git a/test/jsep.test.js b/test/jsep.test.js
@@ -19,6 +19,10 @@ import {testParser, testOpExpression, esprimaComparisonTest, resetJsepDefaults}
 			},
 		}, assert);
 		testParser('Δέλτα', { name: 'Δέλτα' }, assert);
+		testParser('a?.b?.(arg)?.[c] ?. d', {
+			type: 'MemberExpression',
+			optional: true,
+		}, assert);
 	});
 
 	QUnit.test('Function Calls', function (assert) {