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Estraverse (estraverse) isECMAScripttraversal functions fromesmangle project.

You can find usage docs atwiki page.

The following code will output all variables declared at the root of a file.

estraverse.traverse(ast,{enter:function(node,parent){if(node.type=='FunctionExpression'||node.type=='FunctionDeclaration')returnestraverse.VisitorOption.Skip;},leave:function(node,parent){if(node.type=='VariableDeclarator')console.log(node.id.name);}});

We can usethis.skip,this.remove andthis.break functions instead of using Skip, Remove and Break.

estraverse.traverse(ast,{enter:function(node){this.break();}});

And estraverse providesestraverse.replace function. When returning node fromenter/leave, current node is replaced with it.

result=estraverse.replace(tree,{enter:function(node){// Replace it with replaced.if(node.type==='Literal')returnreplaced;}});

By passingvisitor.keys mapping, we can extend estraverse traversing functionality.

// This tree contains a user-defined `TestExpression` node.vartree={type:'TestExpression',// This 'argument' is the property containing the other **node**.argument:{type:'Literal',value:20},// This 'extended' is the property not containing the other **node**.extended:true};estraverse.traverse(tree,{enter:function(node){},// Extending the existing traversing rules.keys:{// TargetNodeName: [ 'keys', 'containing', 'the', 'other', '**node**' ]TestExpression:['argument']}});

By passingvisitor.fallback option, we can control the behavior when encountering unknown nodes.

// This tree contains a user-defined `TestExpression` node.vartree={type:'TestExpression',// This 'argument' is the property containing the other **node**.argument:{type:'Literal',value:20},// This 'extended' is the property not containing the other **node**.extended:true};estraverse.traverse(tree,{enter:function(node){},// Iterating the child **nodes** of unknown nodes.fallback:'iteration'});

Whenvisitor.fallback is a function, we can determine which keys to visit on each node.

// This tree contains a user-defined `TestExpression` node.vartree={type:'TestExpression',// This 'argument' is the property containing the other **node**.argument:{type:'Literal',value:20},// This 'extended' is the property not containing the other **node**.extended:true};estraverse.traverse(tree,{enter:function(node){},// Skip the `argument` property of each nodefallback:function(node){returnObject.keys(node).filter(function(key){returnkey!=='argument';});}});

Copyright (C) 2012-2016Yusuke Suzuki(twitter:@Constellation) and other contributors.

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