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Closure Compiler is a JavaScript optimizing compiler. It parses your
JavaScript, analyzes it, removes dead code and rewrites and minimizes
what's left. It also checks syntax, variable references, and types, and
warns about common JavaScript pitfalls. It is used in many of Google's
JavaScript apps, including Gmail, Google Web Search, Google Maps, and
Google Docs.
/*
* Copyright 2015 The Closure Compiler Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.javascript.jscomp;
import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.rhino.Node;
/**
* Rewrite .bind(this) calls on an anonymous functions to arrow functions
* (which have implicit this binding).
* Remove .bind(this) calls on an arrow function (the bind call here would
* have been useless)
*
* Skips functions that reference the 'arguments' object.
*
*/
class RewriteBindThis extends AbstractPostOrderCallback implements CompilerPass{
AbstractCompiler compiler;
RewriteBindThis(AbstractCompiler compiler) {
this.compiler = compiler;
}
@Override
public void process(Node externs, Node root) {
NodeTraversal.traverseEs6(compiler, root, this);
}
@Override
public void visit(NodeTraversal traversal, Node node, Node parent) {
if (node.isFunction() && canRewriteBinding(node)) {
rewriteBinding(node);
}
}
private boolean hasBindThisCall(Node functionNode) {
Node parentNode = functionNode.getParent();
return parentNode.isGetProp()
&& functionNode.getNext().getString().equals("bind")
&& parentNode.getParent().isCall()
&& parentNode.getNext().isThis();
}
private boolean canRewriteBinding(Node functionNode) {
return functionNode.getFirstChild().getString().isEmpty()
&& hasBindThisCall(functionNode)
&& !NodeUtil.isVarArgsFunction(functionNode);
}
private void rewriteBinding(Node functionNode) {
Node parent = functionNode.getParent();
Node grandparent = parent.getParent();
parent.removeChild(functionNode);
grandparent.getParent().replaceChild(grandparent, functionNode);
functionNode.putBooleanProp(Node.ARROW_FN, true);
compiler.reportCodeChange();
}
}