I want something like this but I have no idea how to do this
https://i.stack.imgur.com/WQfHH.png
var number = document.getElementById('x').value;
var i = 1;
var sum = 0;
while(i <= number){
sum += i;
i++;
}
document.getElementById('html').innerHTML = sum;
const arr = (n) => new Array(n).fill(0).map((_, k) => k + 1);
const calc = (n) => arr(n).reduce((prev, curr) => prev + curr, 0);
const log = (n) => console.log(n, '=>', arr(n).join(' + '), '=', calc(n));
log(3);
log(5);new Array(n) create an array with nth elements.fill(0) fill the array with zeros.map((_, k) => k + 1) fill the array with integer (k is the index of the array, which is zero based).reduce() allow to calculate to sum of every element of the array.join() will concatenate every element of the array to create the x + y partPS: Vincent was quicker but already have redacted my awnser
If the intention is to output number lines, each with 1+2+... = N, you could do:
let output = "";
for (n=1; n <= number; n++)
output += `${
/* "1+2+...+n" */
Array(n).fill().map((_,i) => i+1).join("+")
} = ${
/* the sum */
n * (n+1) / 2
}\n`;