javascript reduce find max in array of arrays

Question

I want to find the max number among the first and second elements of each array inside the array of arrays separately:

 function largestOfElements(mainArray) { return mainArray.map(function(subArray) { return subArray.reduce(function(previousLargestNumber, currentLargestNumber) { return (currentLargestNumber > previousLargestNumber) ? currentLargestNumber : previousLargestNumber; }, 0); }); } console.log(largestOfElements([ [], [13, 47], [38, 35], [24, 34] ])); 

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the current way returns an array of the largest numbers in each array. How can I return the largest of the first elements and the largest of the second elements? the expected result will be:

[38, 47]

Answer 1

You can use the function reduce .

• The initial value for the function reduce are the min values to start getting the highest values.
• Check for the length of the current array.
• Use destructuring assignment to get the first and second value [first, second].
• Check the current value against first and second respectively to get the highest.

 var array = [ [], [13, 47], [38, 35], [24, 34] ]; var result = Object.values(array.reduce((a, c) => { if (c.length) { var [first, second] = c; if (first > af) af = first; if (second > as) as = second; } return a; }, {f: Number.MIN_VALUE, s: Number.MIN_VALUE})); console.log(result); 

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