(ast, visitor)
| 728 | // So we define a traverser function which accepts an AST and a |
| 729 | // visitor. Inside we're going to define two functions... |
| 730 | function traverser(ast, visitor) { |
| 731 | |
| 732 | // A `traverseArray` function that will allow us to iterate over an array and |
| 733 | // call the next function that we will define: `traverseNode`. |
| 734 | function traverseArray(array, parent) { |
| 735 | array.forEach(child => { |
| 736 | traverseNode(child, parent); |
| 737 | }); |
| 738 | } |
| 739 | |
| 740 | // `traverseNode` will accept a `node` and its `parent` node. So that it can |
| 741 | // pass both to our visitor methods. |
| 742 | function traverseNode(node, parent) { |
| 743 | |
| 744 | // We start by testing for the existence of a method on the visitor with a |
| 745 | // matching `type`. |
| 746 | let methods = visitor[node.type]; |
| 747 | |
| 748 | // If there is an `enter` method for this node type we'll call it with the |
| 749 | // `node` and its `parent`. |
| 750 | if (methods && methods.enter) { |
| 751 | methods.enter(node, parent); |
| 752 | } |
| 753 | |
| 754 | // Next we are going to split things up by the current node type. |
| 755 | switch (node.type) { |
| 756 | |
| 757 | // We'll start with our top level `Program`. Since Program nodes have a |
| 758 | // property named body that has an array of nodes, we will call |
| 759 | // `traverseArray` to traverse down into them. |
| 760 | // |
| 761 | // (Remember that `traverseArray` will in turn call `traverseNode` so we |
| 762 | // are causing the tree to be traversed recursively) |
| 763 | case 'Program': |
| 764 | traverseArray(node.body, node); |
| 765 | break; |
| 766 | |
| 767 | // Next we do the same with `CallExpression` and traverse their `params`. |
| 768 | case 'CallExpression': |
| 769 | traverseArray(node.params, node); |
| 770 | break; |
| 771 | |
| 772 | // In the cases of `NumberLiteral` and `StringLiteral` we don't have any |
| 773 | // child nodes to visit, so we'll just break. |
| 774 | case 'NumberLiteral': |
| 775 | case 'StringLiteral': |
| 776 | break; |
| 777 | |
| 778 | // And again, if we haven't recognized the node type then we'll throw an |
| 779 | // error. |
| 780 | default: |
| 781 | throw new TypeError(node.type); |
| 782 | } |
| 783 | |
| 784 | // If there is an `exit` method for this node type we'll call it with the |
| 785 | // `node` and its `parent`. |
| 786 | if (methods && methods.exit) { |
| 787 | methods.exit(node, parent); |
no test coverage detected