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walk.js
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walk.js
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let shouldSkip;
let shouldAbort;
export default function walk ( ast, { enter, leave }) {
shouldAbort = false;
visit( ast, null, enter, leave );
}
let context = {
skip: () => shouldSkip = true,
abort: () => shouldAbort = true
};
let childKeys = {};
let toString = Object.prototype.toString;
function isArray ( thing ) {
return toString.call( thing ) === '[object Array]';
}
function visit ( node, parent, enter, leave ) {
if ( !node || shouldAbort ) return;
if ( enter ) {
shouldSkip = false;
enter.call( context, node, parent );
if ( shouldSkip || shouldAbort ) return;
}
let keys = childKeys[ node.type ] || (
childKeys[ node.type ] = Object.keys( node ).filter( key => typeof node[ key ] === 'object' )
);
let key, value, i, j;
i = keys.length;
while ( i-- ) {
key = keys[i];
value = node[ key ];
if ( isArray( value ) ) {
j = value.length;
while ( j-- ) {
visit( value[j], node, enter, leave );
}
}
else if ( value && value.type ) {
visit( value, node, enter, leave );
}
}
if ( leave && !shouldAbort ) {
leave( node, parent );
}
}