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JavaScript JavaScript Array Iteration Methods Array Manipulation Practice map()

Posted by Christopher Evans
Christopher Evans
9,896 Points

Cannot read property '2' of undefined.

Don't understand why anything would be undefined here...

app.js 
const daysOfWeek = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];
let abbreviatedDays;

// abbreviatedDays should be: ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"]
// Write your code below
abbreviatedDays = daysOfWeek.map((day) => day[0][1][2]);

1 Answer

Steven Parker
Steven Parker
231,261 Points
Steven Parker
Steven Parker
231,261 Points

The expression "day[0][1][2]" would be a way to index into a 3-dimensional array. But "day" represents a single string from the "daysOfWeek" array. So the first index will refer to a single character, and the next one will be "undefined" (and the third causes the error).

What you probably had in mind was to get three separate characters and concatenate them together, like "day[0]+day[1]+day[2]".