Why it object.anonymous
package.json:
package.json:
{ "name": "SmartConverter", "version": "1.0.0", "main": "./src/js/main.js", "scripts": { "test": "jest --coverage", "build": "webpack --config ./scripts/*/webpack.config.js" }, "repository": "", "author": "raushankumarnitdgp <>", "license": "MIT", "dependencies": { "babel-cli": "^6.24.1", "babel-core": "^6.25.0", "babel-jest": "^20.0.3", "babel-loader": "^7.1.1", "babel-preset-es2015": "^6.24.1", "eslint": "^4.4.1", "jest": "^20.0.4", "jest-cli": "^20.0.4", "regenerator-runtime": "^0.10.5", "webpack": "^3.5.2" }
}2 Answers
The anonymous keyword you see in the error stracktrace is just telling you that the error happened in an anonymous function. Anonymous functions are functions without a name, often used as callbacks but not always. For example:
function main() { myLibrary.doSomething('foo', function() { console.log('I have finished') })
}The function passed to myLibrary.doSomething is an anonymous function. The error you are seeing seems to be happening in the phone.js file, line 20. Check where are you using .length.
I think it might be some props haven't been set yet, for instance, if you have a property called expenses inside ComponentX, but in jest file, you didn't pre-set this expenses property,
eg: <ComponentX />, forgot to pass props into this ComponentX, and Jest couldn't find where the expenses property is, expenses would be undefined, and then undefined.length definitely cause that undefined error.
How can we fix this expenses.length undefined issue?
we can do this: <ComponentX expenses={mockExpenses} />
Now, expenses.length should not be undefined, because of expenses have some data.
