@es-joy/estraverse

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@es-joy/estraverse (estraverse) is
a fork of estraverse.

ECMAScript
traversal functions from esmangle project.

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You can find usage docs at wiki page.

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

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

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

`js
estraverse.traverse(ast, {
enter (node) {
this.break();
}
});
`

And estraverse provides estraverse.replace function. When returning node from enter/leave, current node is replaced with it.

`js
const result = estraverse.replace(tree, {
enter (node) {
// Replace it with replaced.
if (node.type === 'Literal')
return replaced;
}
});
`

By passing visitor.keys mapping, we can extend estraverse traversing functionality.

`js
// This tree contains a user-defined TestExpression node.
const tree = {
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 (node) { },

// Extending the existing traversing rules.
keys: {
// TargetNodeName: [ 'keys', 'containing', 'the', 'other', 'node' ]
TestExpression: ['argument']
}
});
`

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

`js
// This tree contains a user-defined TestExpression node.
const tree = {
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 (node) { },

// Iterating the child nodes of unknown nodes.
fallback: 'iteration'
});
`

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

`js
// This tree contains a user-defined TestExpression node.
const tree = {
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 (node) { },

// Skip the argument property of each node
fallback(node) {
return Object.keys(node).filter((key) => {
return key !== 'argument';
});
}
});
``

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

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.