learn-js/jsintro_pt3

[giscus[bot]]

learn-js/jsintro_pt3

Introduction to JavaScript, part III: Objects and Arrays, in-depth Objects Everything in JavaScript is an object! Except for true, false, simple numbers and strings, null, and u...

https://docs.ctjs.rocks/learn-js/jsintro_pt3.html

[netluke]

In the second example of the Array's reduce method, I get the following error from the compiler:

Array.prototype.reduce() expects a return value from arrow function.

var monstersInTheLevel = waves.reduce((currentStats, wave) => {
for (const monsterGroup of wave.monsters) {
// Initialize a monster group if it hasn't been written to the stats object yet
if (!currentStats[monsterGroup.type]) {
currentStats[monsterGroup.type] = 0;
}
currentStats[monsterGroup.type] += monsterGroup.amount;
}
}, {}); // Start with an empty object

The solution is to add a return to the end of the internal anonymous function:

var monstersInTheLevel = waves.reduce((currentStats, wave) => {
for (const monsterGroup of wave.monsters) {
// Initialize a monster group if it hasn't been written to the stats object yet
if (!currentStats[monsterGroup.type]) {
currentStats[monsterGroup.type] = 0;
}
currentStats[monsterGroup.type] += monsterGroup.amount;
}

return currentStats; // THE MISSING PIECE.

}, {}); // Start with an empty object