TypeError：无法读取node.js中未定义的属性“名称”

Question

function getPaths(pathIds, subCategory, callback){
    var currentCategory = JSON.parse(JSON.stringify(subCategory));
    console.log(currentCategory);
    console.log(currentCategory.name);
    var paths = [];
    var pathDirs = "";
    for (i=0; i<pathIds.length; i++) {
        pathDirs += pathIds[i];
        paths[i] = {dir : pathDirs, name : currentCategory.name};
        currentCategory = currentCategory.categories.find(function(category){
            return category.id = pathIds[i];
        });
    }
    callback(paths);
}   

I am new to js and node.js. I receive the above error and I consider it refers to the currentCategory.name property. When I type console.log (currentCategory), I have the entire object printed including the name property. What could have I done wrong?

Here is the stack trace I got for further info:

D:\repos\onlineStore\borrislava-onlinestore\Backup\Work\node_modules\mongodb\lib\utils.js:132
  throw err;
  ^

TypeError: Cannot read property 'name' of undefined
at getPaths (D:\repos\onlineStore\borrislava-onlinestore\Backup\Work\routes.js:124:54)
at D:\repos\onlineStore\borrislava-onlinestore\Backup\Work\routes.js:24:4
at D:\repos\onlineStore\borrislava-onlinestore\Backup\Work\routes.js:112:3
at result (D:\repos\onlineStore\borrislava-onlinestore\Backup\Work\node_modules\mongodb\lib\utils.js:414:17)
at executeCallback (D:\repos\onlineStore\borrislava-onlinestore\Backup\Work\node_modules\mongodb\lib\utils.js:406:9)
at handleCallback (D:\repos\onlineStore\borrislava-onlinestore\Backup\Work\node_modules\mongodb\lib\utils.js:128:55)
at cursor.close (D:\repos\onlineStore\borrislava-onlinestore\Backup\Work\node_modules\mongodb\lib\operations\cursor_ops.js:218:62)
at handleCallback (D:\repos\onlineStore\borrislava-onlinestore\Backup\Work\node_modules\mongodb\lib\utils.js:128:55)
at completeClose (D:\repos\onlineStore\borrislava-onlinestore\Backup\Work\node_modules\mongodb\lib\cursor.js:887:14)
at _endSession (D:\repos\onlineStore\borrislava-onlinestore\Backup\Work\node_modules\mongodb\lib\cursor.js:898:37)

Answer 1

There are a couple issues in your loop :

for (i=0; i<pathIds.length; i++) {
    pathDirs += pathIds[i];
    paths[i] = {dir : pathDirs, name : currentCategory.name};
    currentCategory = currentCategory.categories.find(function(category){
        return category.id = pathIds[i];
    });
}

1 - Array.prototype.find will return the first element matching the condition in the return clause of the provided function.

If none element matches the condition, undefined is affected to the currentCategory variable. Then, when looping again, currentCategory is undefined and you get :

TypeError : Cannot read property 'name' of undefined

2 - There's also a typo in your return clause. You're setting category.id instead of comparing it to pathIds[i] :

return category.id = pathIds[i]

Are you sure you don't want to compare them instead? Because right now, you're setting category.id and returning it in your function. So, the function you provided to your find will return false if pathIds[i] is equal to 0, and true otherwise. Is that really what you want?