match-ast
Collection of helper functions to verify a AST tree structure.
Usage
Type matchers
Example: verify if a tree represents a JSON.stringify()
call
const isCallExpression isMemberExpression isIdentifier } = ; // Check if the tree represents a `JSON.stringify()` call.const isJsonStringify = ;
Most functions are named isSomething
where Something
is the type of the node (i.e. isIdentifier
checks if node.type === "Identifier"
). They accept a single argument: an object where keys represent the property of a node and the value is a matcher for that property.
The accepted matchers are: a matcher function, primitive values, arrays or functions.
Calling a function with no arguments means it will only assert its type and none of the properties. For types with no properties (i.e. ThisExpression
), arguments are ignored.
For nodes with only a single property (i.e. Identifier
with property name
), you can pass directly the matcher for that property, so you don't have to pass an object with a single property. For example, isIdentifier("foo")
is equivalent to isIdentifier({ name: "foo" })
.
Passing extra properties to a matcher will make it always return false:
// check() will always return false since there's no `name` property in CallExpressionconst check = ;
Other matchers
either
For cases where a node can be one of many values:
const either isIdentifier isMemberExpression = ; // Check if the three is a `JSON.stringify()` or `stringify()` callconst isStringify = ;
Credits
This library consists of helper functions automatically generated on top of the excellent @babel/types
definitions.