为什么使用reduce这个function最后会有一个数组？

Question

I am working on an exercise involving the reduce array method. After the accumulator is returned what is the reason for adding the , [] ? Is it just an empty array? My tests did not pass without it until after viewing the answer and adding it to my function. Thanks!

 function extractValue(arr, key) { return arr.reduce((accum, nextName) => { accum.push(nextName[key]); return accum; }, []); } // const arr = [{name: 'Elie'}, {name: 'Tim'}, {name: 'Matt'}, {name: 'Colt'}] // extractValue(arr,'name') // ['Elie', 'Tim', 'Matt', 'Colt']

Answer 1

Just read the official documentation for the.reduce method https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce

That empty array is the initialValue parameter.