I have array of numbers that decreases, but I want it never to decrease:
const numbers =[0,1,2,3,4,5,1, 2];
Desired result is:
[0, 1, 2, 3, 4, 5, 5, 5]
I know how to achieve it with for loop:
for (let index = 0; index < numbers.length; index++) {
const element = numbers[index];
if (index > 0) {
const prevEl = numbers[index - 1];
if (element < prevEl) {
numbers[index] = prevEl;
}
}
}
But when using map
numbers.map((item, index) => {
const prevEl = numbers[index - 1];
if (item < prevEl) {
return prevEl;
}
return item;
})
const numbers = [0,1,2,3,4,5,1, 2];
const result = numbers.map((item, index) => {
const prevEl = numbers[index - 1];
if (item < prevEl) {
return prevEl;
}
return item;
});
console.log(result); // [0, 1, 2, 3, 4, 5, 5, 2]I get this instead: [0, 1, 2, 3, 4, 5, 5, 2]
What would be the functional way to achieve this?
You could use Math.max between the current and the preceding entries in the list:
const numbers = [0,1,2,3,4,5,1, 2];
result = numbers.map((v, i, a) => Math.max(v, ...a.slice(0, i)))
console.log(result)Note that you could/should just use Math.max(...a.slice(0, i+1)) since v is a[i], I wrote it the way I did for clarity as to what the code is doing.