In a certain specific case, Esprima intentially does not throw an exception (indicating - a parsing error) although the input being parsed contains an invalid syntax. - This is to achieve implementation compatibility with major web browsers. - For further details, refer to the official - ECMAScript 2015 - Language Specification, Section B.3.3 on Block-Level Function - Declarations Web Legacy Compatibility Semantics:
- -- Prior to ECMAScript 2015, the ECMAScript specification did not define the occurrence of - a FunctionDeclaration as an element of a Block statement’s StatementList. - However, support for that form of FunctionDeclaration was an allowable extension and most - browser-hosted ECMAScript implementations permitted them. -- -
This is illustrated in the following simple example:
- -
-var syntax = esprima.parse('if (x) function y() {}');
-
-
- In the above example, Esprima returns a syntax tree for the code - (see the result).
- -According to the specification, declaring a function inside the block - of an If statement is not possible. Yet, this is permitted in web browsers - such as Firefox, Chrome, and many others.
- +Please read the documentation on Browser Compatibility.
From version 2.0, Esprima starts to support new features in ECMAScript 6.
- -Since: version 2.0. Specification: section 14.2.
- -Example code snippet:
- --array.map(x => x * x) -- - -
The corresponding syntax tree:
- -
-{
- "type": "Program",
- "body": [
- {
- "type": "ExpressionStatement",
- "expression": {
- "type": "CallExpression",
- "callee": {
- "type": "MemberExpression",
- "computed": false,
- "object": {
- "type": "Identifier",
- "name": "array"
- },
- "property": {
- "type": "Identifier",
- "name": "map"
- }
- },
- "arguments": [
- {
- "type": "ArrowFunctionExpression",
- "id": null,
- "params": [
- {
- "type": "Identifier",
- "name": "x"
- }
- ],
- "defaults": [],
- "body": {
- "type": "BinaryExpression",
- "operator": "*",
- "left": {
- "type": "Identifier",
- "name": "x"
- },
- "right": {
- "type": "Identifier",
- "name": "x"
- }
- },
- "rest": null,
- "generator": false,
- "expression": true
- }
- ]
- }
- }
- ]
-}
-
-
-Since: version 2.0. Specification: section 14.1.
- -Example code snippet:
- -
-function answer(x = 42) { say(x); }
-
-
-The corresponding syntax tree:
- -
-{
- "type": "Program",
- "body": [
- {
- "type": "FunctionDeclaration",
- "id": {
- "type": "Identifier",
- "name": "answer"
- },
- "params": [
- {
- "type": "Identifier",
- "name": "x"
- }
- ],
- "defaults": [
- {
- "type": "Literal",
- "value": 42,
- "raw": "42"
- }
- ],
- "body": {
- "type": "BlockStatement",
- "body": [
- {
- "type": "ExpressionStatement",
- "expression": {
- "type": "CallExpression",
- "callee": {
- "type": "Identifier",
- "name": "say"
- },
- "arguments": [
- {
- "type": "Identifier",
- "name": "x"
- }
- ]
- }
- }
- ]
- },
- "rest": null,
- "generator": false,
- "expression": false
- }
- ]
-}
-
-
-Since: version 2.0. Specification: section 11.8.4.
- -Example code snippet:
- -
-x = '\u{41}'
-
-
-The corresponding syntax tree:
- -
-{
- "type": "Program",
- "body": [
- {
- "type": "ExpressionStatement",
- "expression": {
- "type": "AssignmentExpression",
- "operator": "=",
- "left": {
- "type": "Identifier",
- "name": "x"
- },
- "right": {
- "type": "Literal",
- "value": "A",
- "raw": "'\\u{41}'"
- }
- }
- }
- ]
-}
-
+ Please read the documentation on the Syntax Tree Format.
Contents
- -Note: Partial ES6 support also exists in the experimental harmony branch. However, this branch has never been officially released and the features are not documented.
diff --git a/doc/index.html b/doc/index.html index c264b8ea4..758565c49 100644 --- a/doc/index.html +++ b/doc/index.html @@ -6,6 +6,7 @@