var rank1 = 0
var rank2 = 0
var rank3 = 0
var rank4 = 0
const array1 = [Rank1, Rank1, Rank1, Rank3]
var Rank1 = Rank1
var Rank2 = Rank2
var Rank3 = Rank3
var Rank4 = Rank4
array1.forEach((Rank1) => {
rank1++
});
array1.forEach((Rank2) => {
rank2++
});
array1.forEach((Rank3) => {
rank3++
});
array1.forEach((Rank4) => {
rank4++
});
I'm trying to loop through array1 and save the number of times each item occurred in the array to their var.
For example, if array contains two Rank1, I want the variable rank1 to be equal to 2.
if i console.log rank1, rank2, rank3, rank4 i get the result 4,4,4,4 instead of the wanted result that would be 3,0,1,0 in this case
In this case it is best to use reduce() on the array. Essentially your starting with an empty object and then you start iterating over the elements in your array. If the value you encounter is unknown, add the value as a property to the object as set its value i.e. its number of occurrences to 1. If you encounter a value that is already know, it must already be in the object, then get that count and increase it by one.
At the end of the loop you will have a count for each value in the array. This algorithm has a runtime complexity of O(n) which is an asymptotically optimal algorithm as the lookup in the object happens in O(1). You could also implement this with a Map, which would essentially be the same algorithm (see below).
You can think of the Map/ JS object as your different count variables rank1, rank2, rank3, .... Only difference is, it scales to however many count variables you need and you pick variable which you need to increase automatically by simply using the value that you want to count.
const array1 = ["Rank1", "Rank1", "Rank1", "Rank3", "Rank2", "Rank4", "Rank1", "Rank3"];
const count = array1.reduce((prev, cur) => {
if(prev.hasOwnProperty(cur)) prev[cur]++;
else prev[cur] = 1;
return prev;
}, {});
console.log(count);Expected output:
{ Rank1: 4, Rank3: 2, Rank2: 1, Rank4: 1 }
const array1 = ["Rank1", "Rank1", "Rank1", "Rank3", "Rank2", "Rank4", "Rank1", "Rank3"];
const count = array1.reduce((prev, cur) => {
if(prev.has(cur)){
let currentCount = prev.get(cur);
currentCount++;
prev.set(cur, currentCount);
}
else prev.set(cur, 1);
return prev;
}, new Map());
console.log([...count.entries()]);[
[
"Rank1",
4
],
[
"Rank3",
2
],
[
"Rank2",
1
],
[
"Rank4",
1
]
]
You can try the following below code.
var rank1 = 0
var rank2 = 0
var rank3 = 0
var rank4 = 0
const array1 = ['rank1','rank1','rank1','rank3']
array1.forEach( function( item, i ) {
eval( item + '+= ' + 1 + ';');
} );
console.log(rank1, rank3);