It's example of array which contains only numbers:
var array = [3.1, 1, 2.2, 5.1, 6, 7.3, 2.1, 9]
How to count how many(edited from word 'sum') of elements are in array below / above given number eg. '5.25'?
So answer should be 5 elements are below (3.1, 1, 2.2, 5.1, 2.1) and 3 element are above (6, 7.3, 9)
Use Array#reduce with an object { above: 0, below: 0 } as initial value. On each iteration check each number against the media, and accordingly add 1 to above/below.
Note: This is an array of strings. I've converted them manually to numbers. I also assume that a number that equals the median should be added to below. If you want to skip this numbers, change the comparison to <.
var array = [3.1, 1, 2.2, 5.1, 6, 7.3, 2.1, 9];
var median = 5.25;
var counts = array.reduce(function(s, n) {
s[n <= median ? 'below' : 'above'] += 1;
return s;
}, { above: 0, below: 0 });
console.log(counts);If you must have an array of strings, you can convert to a number in run time using String#parseFloat or the + operator:
var array = ['3.1', '1', '2.2', '5.1', '6', '7.3', '2.1', '9'];
var median = 5.25;
var counts = array.reduce(function(s, str) {
s[+str <= median ? 'below' : 'above'] += 1;
return s;
}, { above: 0, below: 0 });
console.log(counts);
No need for reduce, because the result does not change by using reduce, it is still an object.
var array = [3.1, 1, 2.2, 5.1, 6, 7.3, 2.1, 9],
value = 5.25,
counts = { below: 0, equal: 0, above: 0 };
array.forEach(function(v) {
counts[{ '-1': 'below', 0: 'equal', 1: 'above' }[Math.sign(v - value)]]++;
});
console.log(counts);Assuming you are using an array of numbers..
I use lodash ...it helps shorten the code &
var array = [3.1, 1, 2.2, 5.1, 6, 7.3, 2.1, 9];
console.log(_.sum(array)); // _.sum does the addition<script src="https://cdn.jsdelivr.net/lodash/4.14.1/lodash.min.js"></script>There are couple of strategies but I will use the one thats easy to read and understand:
(1) Create a new array with all elements that fit the criteria aka <=5.25
let sampleArr = ['3.1', '1', '2.2', '5.1', '6', '7.3', '2.1', '9'];
let sortedArr = sampleArr.filter(function(e){
return parseInt(e) <= 5.25
});
Notice I wrote parseInt(e), that converts the string into a number. The values you gave in your array were all strings.
(2) Now simply get the length of the sortedArr like so:
let finalCount = sortedArr.length;
Hope this helps!
.filter and count length of sortedArr. Thanks