"Encountering a hiccup in executing map.reduce

Question

"Encountering a hiccup in executing map.reduce

var mapFunction1 = function() {

    for (var i = 0; i < this.money.length; i++) {
        emit("balance", this.money[i].amount);
    }

};

var reduceFunction1 = function(keyBalance, valuesBalance) {
    return Array.sum(valuesBalance);
};

db.users.mapReduce(mapFunction1, reduceFunction1, {
    out : "balance"
})

db.balance.find()

However, an error has occurred

uncaught exception: map reduce failed:{ "errmsg" : "exception: TypeError: Cannot read property 'length' of undefined\n at _funcs1 (_funcs1:2:37) near 'is.money.length; i++) ' (line 2)", "code" : 16722, "ok" : 0

javascript mongodb mongodb-query

Answer 1

Answer №1

This situation indicates that the property "length" is undefined on an object within your document, most likely because the property does not exist.

When running JavaScript evaluations in a mapReduce process, it is important to be thorough and "strict" in testing for these conditions:

var mapFunction1 = function() {
   if ( this.hasOwnProperty("account") {
       for (var idx = 0; idx < this.account.length; idx++) {
           emit("saldo", this.account[idx].balance);
       }
   }
}

Using .hasOwnProperty() is essential to prevent such errors by verifying the existence of the object.

Answer 2

This situation indicates that the property "length" is undefined on an object within your document, most likely because the property does not exist.

When running JavaScript evaluations in a mapReduce process, it is important to be thorough and "strict" in testing for these conditions:

var mapFunction1 = function() {
   if ( this.hasOwnProperty("account") {
       for (var idx = 0; idx < this.account.length; idx++) {
           emit("saldo", this.account[idx].balance);
       }
   }
}

Using .hasOwnProperty() is essential to prevent such errors by verifying the existence of the object.

"Encountering a hiccup in executing map.reduce

Answer №1

Similar questions

JQuery - Triggering $(document).ready() before the elements are fully loaded

Adding images to chart labels in vue-chartjs explained

Invoking PHP code from within Javascript will output the function as a direct string

The custom error message E11000 is specific to MongoDB's unique index constraint

Extract form input to utilize in nodemailer

What is the method for accessing a map that has been set in a separate component?

Searching through an array based on a specific string

"Encountered a 'NextAuth expression cannot be called' error

In JavaScript, when a div element contains an iframe, the click event will not trigger on the div

Include @url.action with a parameter on a cell within a table using AJAX

I'm attempting to retrieve external XML data and showcase it on my HTML page

The three.js raycaster is able to detect objects both in front of and behind the specific object I am trying to select

Unable to locate 'this' in the callback function triggered by tinymce

I am selecting specific items from a list to display only 4 on my webpage

Even when only a handful of modules are utilized, Webpack still imports a significantly large existing chunk

Picking out specific SharePoint components using jQuery

Ways to verify if a variable holds a JSON object or a string

One way to concatenate texts in an array of dictionaries while keeping the order intact in JS/React is to compare and match specific key-value pairs

Is it possible to pass a useState function to a component during its initialization?

Is it possible for links to remain clickable even if they pass underneath a div