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files >> //opt/alt/alt-nodejs19/root/lib/node_modules/npm/node_modules/treeverse/lib/depth.js
// Perform a depth-first walk of a tree. // // `visit(node)` is called when the node is first encountered. // `leave(node, children)` is called when all of the node's children // have been left or (in the case of cyclic graphs) visited. // // Only one of visit or leave is required. (Technically both are optional, // but if you don't provide at least one, the tree is just walked without // doing anything, which is a bit pointless.) If visit is provided, and // leave is not, then this is a root->leaf traversal. If leave is provided, // and visit is not, then it's leaf->root. Both can be provided for a // map-reduce operation. // // If either visit or leave return a Promise for any node, then the // walk returns a Promise. const depthDescent = require('./depth-descent.js') const depth = ({ visit, leave, filter = () => true, seen = new Map(), getChildren, tree, }) => { if (!leave) { return depthDescent({ visit, filter, getChildren, tree }) } if (seen.has(tree)) { return seen.get(tree) } seen.set(tree, null) const visitNode = () => { const res = visit ? visit(tree) : tree if (isPromise(res)) { const fullResult = res.then(resThen => { seen.set(tree, resThen) return kidNodes() }) seen.set(tree, fullResult) return fullResult } else { seen.set(tree, res) return kidNodes() } } const kidNodes = () => { const kids = getChildren(tree, seen.get(tree)) return isPromise(kids) ? kids.then(processKids) : processKids(kids) } const processKids = nodes => { const kids = (nodes || []).filter(filter).map(kid => depth({ visit, leave, filter, seen, getChildren, tree: kid })) return kids.some(isPromise) ? Promise.all(kids).then(leaveNode) : leaveNode(kids) } const leaveNode = kids => { const res = leave(seen.get(tree), kids) seen.set(tree, res) // if it's a promise at this point, the caller deals with it return res } return visitNode() } const isPromise = p => p && typeof p.then === 'function' module.exports = depth
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